PS3typeS

I just bought this nice 2003 TL type S. I love the car and I am slowly fixing the little things, well this is annoying. First I looked at the battery and there were two extra wires connected to it, I disconnected those. In the trunk there are several wires coming through that are not connected to any sound equipment that must have been removed; subs, amp, etc. I see aftermarket wires so I decided to take out the after market head unit, an Alpine CDA. there is a mess of wires some for two labeled for subs, the other two sets of two wires not labeled but aftermarket monster or whatever wires. I put it all back made sure no crimps were undone or anything and the wires all looked fine, but still no matter what I fiddled with: no sound. Anyone with some advice? Should I just try and get a stock headunit for cheap? Im not sure what to do to trouble shoot a radio problem I know nothing of this area. Thanks for any help!