Spend some time reading on
Trillium belly band. You don't need the black rubber, the entire band needs to be removed with some
fiberglass work.
Windows need to be removed, new seal material installed, rotten wood replaced, and
windows reinstalled. Once complete the black screw cover is readily available.
Trilliums are great but have some well known shortcomings many have addressed. Check out the manufacturers tab on the top right of the screen and then click on
Trillium. Read the various threads and you will learn a lot very quickly.
Lights can be anything from bad converter, to wiring, to bulbs, to you name it. If you have the original power center, its 40 years and at the end of its life. Various threads on power center replacement too.
Appliances are not unique to Trillium, so the same folks that repair RV appliances should be able to fix yours. Do realize the Trillium had a small
refrigerator, no replacements out there that fit without cabinet being modified. So keeping the old one up and running is the best option.