I'll see if I can help some. I use to have and tow trailers with a 1998 and a 2002 Tahoe, very similar to your Yukon. And I do not know if your have the short Yukon or the XL longer one. I agree, having a WD hitch will greatly help the ride and stability of the truck. You put any kind of cargo in the back of the truck and then hang a camper on the back and it's hurt'in.
I see you have a 2007. This is the GM 2007 redesign receiver
And yes it is up there.... You mentioned a 6" drop shank, well it may not be enough. See here. This is a 6" drop shank on my 2003 K2500 Suburban where the receiver was under the bumper. The 6" lowers from the top of the shank to the top of the ball platform on the WD hitch head.
To figure out the drop, here is a rough way to get you in the league. Level up the camper on level ground. I'm assuming you have a tow ball as you somehow got the camper home. Put the ball up in the ball coupler of the camper when it is level so you can measure from the flat spot on the ball where it mounts to the hitch head to the ground. OR just measure the top of ball to the flanged area that goes up in the ball coupler. Many "standard" tow ball are in the 3 3/8" range for this dimension but not all of them. So you have to check
This is a "busy" pic but is one I helped Medbill here on the forum work through his long drop shank.
And this was his shank
When they advertize in a catalog a 6" drop shank, it does not mean it is 6" long, it means it lowers the ball mounting surface 6" from the "top" of the 2" WD shank. This confuses many including RV parts guys.
Here you can see 1 1/4" drop on the standard Reese shank.
And here is the physical 6" drop shank from my Suburban. it is 12" long but is made to drop a "trunnion bar" hitch head 6"
The hitch head eats up 6" of the shank just mounting the head
OK so that is how they rate the drop of a shank in the catalogs of hitch manufactures. There is "often" a difference in the amount of drop between a trunnion bar WD hitch head and a round bar WD hitch head. It depends on the brand of WD hitch. So heads up, you need to know what style and what brand of WD hitch you are buying the drop shank for when you go looking. The hitch heads are made different sometimes in the mounting holes to the ball platform.
And then there is truck squat. A WD hitch properly setup will allow the truck to squat 1" to 1.5" as a good estimate. That lowers the the truck receiver and helps reduce the amount of drop shank on "non air ride" rear suspension. See here, this is the truck squat I'm referring to not hooked up. The truck will be lower when hitched
BUT, you have auto ride rear suspension and this adds a new dynamic as the truck when turned on is going to pump back up to normal ride height no matter what you do. There is a tolerance it comes back up to, maybe +/- 1/2", I do not know on your truck. Odds are high you will have very little truck squat to compensate for with rear air suspension.
I typed the above to help explain where all this is coming from and to help save you from having to buy 2 shanks. The 1st one wrong and the 2nd one right...
In your case with rear air suspension, turn the truck on, let it come up to normal ride height. Measure from the top of the 2" receiver hole to the ground when the truck is level. Then measure the camper when it is level from the flange on the tow ball that would mount on top of the WD hitch ball mount. Subtract the 2 numbers and that is the approx drop shank you need. Odds are high it may be a 9" drop if you have a real low rider Sunline. Some where setup on 18.5" ball height, some 17.5 and some 15.5. Your high up receiver hole is "up there"
Hope this helps and glad to help more when you get into it.
The post Henry linked you too is a good one to help get you started.