Any time I acquire an unknown used camper, I do a LP gas check on it. There are 3 tests to do, one for leaks, one that the LP gas pressure is correct, and a 3rd test to make sure the main tank regulator will regulate the gas pressure correctly when all appliances are running. You really will not know if all 3 will pass unless you have them tested.
The RV, LP gas components do have some level of wear, but age and corrosion happens on the bare aluminum parts more often on the gas valves and rubber deterioration in the pressure regulators/valves.
These checks need to be done by someone with the right test equipment and understanding of the LP systems. If you have a friend who repair home gas systems, they have the test equipment and this is a standard gas test. I'm not sure what this might cost at a RV repair place, the test is fairly quick but what they find, and most all the time they will find something on an old camper, troubleshooting and repairing the parts that do not pass, can add up in cost.
Point being, Yes, in my opinion anyone who acquires a used camper should have the LP system tested. It was good of you to think of this.
This is a generic explanation of the LP system. I am not sure which exact gas appliance models you have in your 96 Solaris. You can find the model number tags on each device. The range tag (an Atwood/Wedgewood Or Camp Chef in some cases) range tag is normally under the top cover over the burners inside the camper.
The water heater, an Atwood brand heater, the name tag is outside the camper behind the drop down door.
The fridge uses LP gas, and the name tag, Dometic, is inside the fridge compartment inside the camper on the side pillar near the edge of the door.
The furnace, Atwood Hydroflame, well it depends on the model you have, If there is a large cover plate (approx. 8" x 12 - 15" long, outside the camper where the furnace exhaust vent is, behind that cover (4 screws) is the model tag.
If the furnace has a smaller outside exhaust plate, about 4 - 5" wide x approx. 6 - 8 "lg. and no easy removable cover, I "believe" the model tag is inside the camper behind the furnace grill plate.
If you have the make and model of each of them, our files section has most of the manufacture owners manuals to you can down load a copy of. If we do not have them there, we can help you find them on line.
The big picture of how the LP gas delivery system works, starts with the LP tank or tanks on the front of the camper A frame. Some have 2 tanks, smaller campers have 1 tank. The 2 tanks system can have a "change over" main tank regulator that automatically switches from the main tank to the back up tank when the main tank runs out of gas. Assuming, the back up tank valve is open.
The single tank, still has a main tank regulator. The purpose of the main tank regulator is to drop the high tank pressure (~100-150psi) pressure down to a low pressure (11" water column (WC) approx. 0.5 psi) pressure. The camper main tank regulator is considered a 2 stage low pressure regulator due to having indoor LP gas appliances. This regulator and pressure is different (lower pressure) then a standard outdoor gas barbeque grill which many are considered high pressure (5 to 8psi) .
The low pressure gas from the main LP tank flows through a flexible hose near the tank to a ridged steel distribution pipe under the camper. The rigid pipe runs under the camper and tee's off to each appliance, normally with soft copper tubing going up through the camper floor.
Each gas appliance has it's own integral on/off gas valve system. The main LP tank valves when open, allow gas to flow up to each appliance through the rigid pipe distribution system. Each appliance then turns on and off the gas as needed when the appliance is turned on by you.
I "think" your camper is new enough that the hoses that hook up the LP tank have a green or black plastic coupling nut on them. These newer plastic coupling nuts (right hand thread) have an excess flow gas safety valve inside them. These coupling nuts look like this. They are green in this pic that screw onto the LP tank. This pic also has the auto change over regulator in the pic.
If your tank has the older all brass hex nut (left hand thread) that screws into the tank (no plastic nut) then they have a small office in them but not the excess flow safety valve.
When you open the main LP tank, slowly, very slowly open the valve a little, you will hear a slight hiss of gas flowing and then it will stop hissing. When the hissing stops, open the valve all the way until it stops at full open. You open it all the way to create a seal inside the main tank valve so the gas does not leak out around the valve stem. Stopping part way open, on an older tank, the gas may leak out slowly at the valve stem.
The excess flow valve inside the plastic coupling nut has a safety feature to only allow a predetermined amount of gas through the valve. The plastic nut color determines the capacity of the valve. The black valve is lower capacity then the green nut. This restricting device helps in the event of a major appliance or hose leak down stream of the main tank, to not release large amounts of gas to worsen the safety issue of leaking gas. If you open the tank valve fast, that safety device will trip and highly restrict the gas coming out and the gas appliances will/may not work right pending what you are doing. They will act like the tank valve is not open very far. If you accidently trip the safety valve (it happens), you need to reset the safety valve and try again. The safety valve resets when gas pressure upstream and downstream of it is close to equal. There are a few way do do this.
First method, this may be the fastest way.
1A. Shut off the main LP tank valve,
2A. Remove the tank coupling nut from the tank and bleed out the gas pressure.
3A. Put the tank coupling nut back on and try again to slowly open the tank valve.
1B. Shut off the main LP tank valve,
2.B. Go inside the camper, open a window near the stove, with a grill lighter, try and light a stove top burner. Any and all gas pressure will bleed out the burner. The burner may or may not light.
3A. When no more pressure/gas is coming out the burner, shut the burner off, go outside and try again to slowly open the tank valve.
Third method. This may be the slowest way, but nothing has to be done but wait.
1C. Shut off the main LP tank valve.
2C. Wait, and listen closely at the tank valve. You might hear a soft "click". The click, if you can heat it, is the safety valve resetting. If you hear it, then:
3C. Try again to slowly open the tank valve.
Method 3 is the simplest to do, but there is no specific time for the system to stabilize in pressure on both sides of the safety valve. The time depends on how charged the camper system was with pressure at the time the safety valve tripped. And you might not hear the click. But it is simple to do, and if you did not wait long enough, the safety will not reset and get stuck again in the safety position when you open up the tank valve. No harm done, just start over at step 1C and try again.
Those are the basics. Ask for more on specifics you need help with.
Hope this helps