The seats are pretty easy to rebuild/ refurbish. It takes a lot of time though. You could check for used seat frame parts and fix that up for the start. Everything else is pretty much easy as pie. Even if you have falling apart coco-pads they can be used and built up with spray rubber and foam. I reused my pads which were crumbling. After the many coatings of flex rubber spray I then glued foam to them and cut the shape correctly with razors, lots of them. It was very time consuming, but not hard. I have posts here on the SL forum about the project.
http://www.peachparts.com/shopforum/sl-forum/343119-seat-refurbishing.html