Sounds like structural issues all around--the kitchen/living room wall is probably do-able but you'd need an engineer to check it out for you. They make some fabulous laminated beams these days if you can afford to totally open it up, OR you can leave some pillars in place to hold up the existing beams, but that may affect the look you are going for. FWIW we left the wall between our kitchen and living room for similar reasons.
Your attic is probably not inhabitable at this point, it sounds like they totally re-did the roof when they put in the trusses and you'd need to rip it off and re-build to change it back

Our house had a shallow hip roof (slanted on all four sides) so there was no going up in our case even though we didn't have trusses.
The bathroom sounds
totally promising for a DIY fix though
When you are ready, a tub surround is an easy replacement unless you need to replace the tub as well. Just pull those plastic panels down, pull off any old drywall or green board, and screw up cement board in its place (with stainless steel screws) and then glue on something nice like
Barkerboard or go whole hog and tile over it

There are lots of books that will give you the basics on tiling, start with your kitchen back splash to try it out
A retro pink tub/sink/toilet set can work really well with the right paint colours and tile/flooring, we only had the tub left in pink--the toilet and sink had been replaced before we bought and there was no way to match the tub colour anymore so we had ours re-coated to be white.
If there is any mold, it is likely only in the drywall (older house so very possible that this is all that's behind your plastic panels) or green board (if the surround was put in during the 70s remodel you might be lucky and have green board which is mold-resistant drywall).
The carpet is likely over top of vinyl flooring, so just peel up a corner and check. If so, you'll have a new floor in short order just be getting rid of the carpet. If it's over the plywood subfloor, you'll need to pull it up and put in a new floor. Tile is easy, but more expensive, and you can do it by the book. The tile guys at your Lowe's should have great advice as well. Otherwise go with vinyl. You can do peel & stick tiles or sheet vinyl, both are pretty easy and just get stuck/glued down--again by the book.
If your vanity is tired/dated, just paint it--you can buy counter top paint as well for a quick and cheap fix until you can put in something you like better
