Well to answer your first question there is an interface you can buy and I think it workd with all decks that will allow you to still use your steering controls. It is roughly 50-75 dollars. I wanted the same thing but I decided that the extra wasn't worth it so I bought a deck with a remote. As far as deck goes mine has a usb input ( i put 200+ songs on a thumb drive and use that) but it also has an ipod hookup. Got it for $200 its a Kenwood if that helps you at all.
for your second question a lot of people will tell you that you really can't build big power without big money. The good mods are all over pretty much $300. i am broke so I am going the slow route with cheapo parts. Intake, PCM, used parts from the for sale ads that kind of stuff. The best bang for your buck is probably the top end swap. If you want better brakes check the ads for the f-body brake upgrade they are a great price at just over $200. Happy modding!
