Looking for some parts...

Rust on the rocker panels, door bottoms is VERY common, repair panels are available and not expensive. The rear barn door hinges are a poor design, you WILL have trouble with them, they can be repaired easily or replaced. The front idler arms and tie rod ends tend to wear out in 50K or so, again not hard to replace. They wallow some in the wind. The engine is not hard to service if you do it from inside the van by taking the doghouse off.

Carpet wise it would be easier to do what the conversion van builders do, Use a couple of sheets of plywood to make a smooth floor and glue indoor/outdoor carpet to it. The seats depends on which mounting system you have, some were just bolted in, others used brackets in the floor and locked the seats into them. If you have the bolt down type they are easily found in salvage yards. You need to decide what type of seat you want, then just bolt them in.