Installing a new radio in a 04 trail blazer

[Retired Racer]

I bought a Kenwood radio for my Blazer. Me and a friend installed it. It worked at first but the gas gauge went down. So we changed the wires around and got it to work again. All of the sudden it quit working. We messed around with it and couldn't get it to work. We decided to put the old one back in. We got it back together and now the old radio won't work either. Its not the anti theft either. I read about that in the owners manual. IIs there a fuse some where that I am missing? Please help me out.