318ti.org forum - Aftermarket antenna question

I bought an aftermarket antenna from autozone. The kind that stick to your window. Its an amplified antenna. Currently where I'm living, my antenna only picks up one radio station frequency. Apparently someone tried to yank out and steal the antenna from the previous owner which left me with nothing. I'm trying to fix it by installing this new antenna. I figured instead of running a new antenna wire to the radio, I'd splice the antenna wire from the previous antenna over to this one and use the wire thats routed within the car. I wanted to ask if anyone has had any experience doing this before, and their tips and suggestions. Also I'm trying to find a 12v power source in the rear that I can splice into to power the antenna's amplifier. Any help? :D