1. take it to any muffler shop and have them weld it... not something you want to do to your own car if you haven't learned on scap first.
2. just replace the tranny... plenty of people on here do part outs.
3. PepBoy, O'riely's, etc... they sell exhaust wrap. Take the part off your going to wrap (exhaust, mani, down pipe)... take the entire roll of wrap and put it in a bucket of water and let it soak. It wont fall apart but it will become slightly more elastic and alow for a tighter wrap. Start at the back and work forward, the reason for this is wind under your car isn't hitting an open layer. Wrap should lay 1/2 over 1/2, and use the metal ties to secure it in place, 2 on the start point and 2 on the end.
Carpet will make you life so much nicer.
New Nissan 240SX Molded Carpet Interior Replacement Kit
4.
http://zilvia.net/f/s-chassis/395413...-pictures.html
5. When you get a Trany this will be part of it. Replace your Lower harness also it sounds like your car has gremlins.
6. Energy Suspension sells a bushing kit. There is a "how to" floating around but its on the evil nissan forum.
7. find it in a part out thread or buy a new Stainless Steel braided one from ChaseBays, etc...
8. This is really a pain in the ass but its almost easyier to just buy an uncut Engine Harness (Upper and Lower) and Chassis Harness. find it in a part out thread and ask for the sensors. When you get them in, you should clean all of them with Brake Clean!!!
If you dont mind take some pics of the car...