Hi, trying to find info on amp installation for 03 Sunfire.

I tried searching through the forums and other webpages (google ect...) and can't seem to find exactly what im looking for.

If this sounds familiar to anyone and has a site I would appreciate it or appreciate any help anyone could give me.

Im trying to hook up a 4 channel amp to my stock HU.

I know about the harness and I dont care about the chimes.
What I do know is:

1)Power from battery hook to amp
2)RCA cables have to go from amp to HU
What would I use since the stock HU doesn't have RCA holes? I saw someone said somethign about a in line coverter from Walmart, a Schoche or something. Would that work?
3)Speaker wires from the speakers to the amp
4) 12V wire, no clue on this.
5)Ground wire goes to metal
6) Remote turn on from amp to HU

I havent bought anything yet, but have searched for what I need.
I plan on replacing the 2 speakers in the door and in the rear before installing the amp.

Does anyone have a detail guide on to install an amp to the HU for a 03 sunfire or class 2 system?

Car electronics different from computer electronics --.--

Appreciate any help.

Oh, and the amp im looking at buying has

High/Low pass crossovers
Line/Speaker inputs

If that has anything to do with installation.