I do believe the shock mount stud is a dealer item only. It's up to you as far as plastic or steel for the tank. Use a thick piece of rubber or a wide belt between the tank and skidplate to protect from rubbing and moisture (for steel tank). This is the ideal time to replace your fuel pump and sending unit assembly, too.
If you have a skid plate underneath the stock gas tank, the 8 bolts holding it and the tank to the frame will be a PITA to remove. I might have a recent post ranting about my troubles, but I found the secret to removing the bolts without stripping all of them. Use a 1/2- drive break-over bar and 15mm socket to turn the bolts, and hold the nuts with a quality a 15mm wrench. If you try to use a socket or wrench to turn the nuts, they are very soft and will strip. I had to remove the rear bumper, too.
I'm pulling all of this stuff out to restore the frame. If you have some rust, look at using something to stop it from getting worse. I'm using Ospho since it's cheap, JSM84
Cleaning & Rustproofing Frame