you'll need a line output converter, wire it into the speaker leads at the deck. You'll then need to wire your remote turn on into the accy turn on for the factory deck and fuse it. Then run your amp kit (rca's, power wire, ground wire etc like normal).
I'm an MECP installer at best buy and with our current prices, what i'd charge would be 90 labor and 15 for loc and then the price of the amp kit.
Personally well worth it and way under $200 plus you get a lifetime warranty on the labor. Anything goes wrong, you're covered.