Hi
Me too just picked up a 1987
Cadet, today I gutted the whole thing down to the Fiberglas, it had the original red velvety stuff on the roof and walls, looked like a brothel on wheels.
I removed all benches, counter , closet and upper cupboards and shelving.
Ripped out the old Lino even though it looked pretty good but when I started yanking on it the plywood underneath had mold, So I will be replacing that.
The trailer came with a brand new roll of foam backed vinyl but the colour is gold / mustardy so we are thinking of installing it and then paint the vinyl.
To remove the benches and cupboards and kitchen cabinets it was a real pain in the ars, them polish people used the stupid screws where you need a flat blade screwdriver.
So to answer your question, for the double bed just keep the rear table down and keep that as a bed that what we will be doing.
If the stove and sink still work I would leave it and cover it, if sell down the road others might like a stove, and too if the weather is crappy at least you can make your self a cup of coffee or bowl of soup.
As for cushion covers you can get cushion covers on Amazon they slip right over the old cushion just get the right size.( we did this in our big camper )
For the wall coverings I would leave it an see if you can clean it with dawn dish soap, it really doesn’t look that bad.
For paint the cupboards you would need to sand them down as the veneer is pretty shiny, use a bonding paint first or Kilz and then use a good latex paint.
Other than that congratulations on your new camper, they are super
light and easy to tow.