First off, welcome to the community! There is a TON of useful information on this website so be sure to take advantage!!!
When it comes to your squeak under the dash when the climate control is on; sounds like your blower motor is bad. Pretty common problem when water gets into the blower motor, probably from your clogged cowl. Do a search and like I said, it's an easy fix.
The pop of the tranny in reverse is something I'm not familiar with, but the guys over in the transmission section are pretty good, and usually will help you troubleshoot.
Basic beginner mod ideas can be found in the L67/L32 section. Great place to start. Look at the stickies.
