I read your last post in the intro forum and now this one here. I looked at the pics you posted. I will comment in this one post for you.
I will echo PTHutch's response, as for the financial side of this, doing the rebuild yourself is the practical way to do it, especially with Allan's skill set and your help. Hiring this out due to the large labor cost can cost more then the camper is valued at or what you may be able to sell it for.
From your pic I can see the ceiling damage which points to a water infection in the roof that is either very large or is small but has been on going for I would estimate 2 to 3 years or more. By the time you see the damage show up inside like that on a "slow" leak, the leak has been on going for a good 2 - 3 years, maybe more, as the leaks grew in size over time. And the roof leak allows water in which seak's the lowest point it can go. Odds are your front wall and some of the side walls near it have some damage.
Many here on the forum has been through this and their campers now look great!
I myself acquired a "project camper" (the 2004 T1950) this year too that is not as advanced as yours, but will be using just about the same repair process. I knew what I was getting into when I acquired it, but I know these Sunny's can be restored to their full glory in time. In my case the rear wall board is in need of replacing verses the ceiling. And then there will be other repairs up in the roof with rafter correction and under the camper dealing with trapped water in the underbelly. I have not started the disassembly process yet, I may within the next month to just open it up and let it dry out. The rebuild itself may need to wait until winter time with everything else we have going on.
When the rains stop, I agree if you can, cover the camper to stop more water from getting in. Letting more in, makes what you have worse. However while covered, it has been shown that wet trapped in the ceiling, walls or under the camper above the black waterproof membrane (we call this the Darco underbelly covering) will stay that way until you open it up and let the open air start the evaporation process. The batt insulation acts like a sponge and soaks up a lot of water that will not evaporate out. And the rubber roof will not let evaporation go up and out, nor the siding. The water is trapped in there... Or it is will take a really long time, maybe a year or more if then. And if it did evaporate out, odds are likely a dry rot fungus has started which is as bad as the wet rot. The dry rot leaves you with dust of a beam looking thing rather then wet rot which is a soggy mess.
When you open it up, it is going to look really ugly... and that it seems hopeless, especially seeing this for the first time. But... don't despair it can be brought back to life after you get the wet yuk out. When the camper dries out, it actually starts looking better. And it all gets better after each work day from there!
This will take time to do but when you are all done, the camper can be a really great unit you can keep as long as you want. There is a real good feeling of pride when you are out camping is a restored camper. We really get attached to these campers... trust me.
A year ago, my son and I redid a 2006 T264SR that ended up having 3 roof leak areas. The inside was still perfect, but the damage above the ceiling and rear walls was there. That camper is now in perfect condition with a full walk on roof better then my good T310SR. He also took it further this year and Eternabonded all the roof seams to not have this issue happen again.
That camper will last him a life time now if it wants it that long and it is taken care of from here forward. This post documents the process and the costs along with the hours it took the 2 of us to get it done. While yours will be a little more dealing with the inside ceiling, what is in this post is very applicable. And your camper is smaller so that helps too.
By your pics, the cabinets and other things in the camper still look in pretty good shape unless there is a photo anomaly going on. What you have is a "project camper" but you can turn it into a real gem when you are done.
One thing that does help, take lot of pics (detail and far away) of every stage of the disassembly process. It helps when you start rebuilding, h'mm what did that look like? Those details come in handy when you start the fix it portion of the project. And you can share them with us so we can help see what you are up against and suggest how to make the repair.
Hope this helps. We are here rooting for ya!!