amp, subwoofers with stock ford hu

Hey everyone Im new to the forum and to car audio in general so forgive me for asking dumb questions. Is it possible to wire my amp and subwoofers into a stock ford stereo. Its doesn't have the rca amp pre-outs. I assume there is a way to splice the speaker wires into the stock wire harness, but I don't have any idea which wires to use. If anyone has experience with ford wiring or knows a website that goes over this I would really appreciate your help. Here is a link to a dash unit like the one i have. another quick question is about wire gauge. I have a whole lot of 14 gauge wiring laying around and I was wondering if instead of buying 8 gauge wire (which I can only seem to find in 50 or 100ft spools for like 20-30 dollars) I could just use 2 (or maybe 3) 14 gauge wires. I assume this would be enough to handle the wattage right. My amp is only 700 watts. Let me know and thanks for helping me out.

to answer your main question about wiring a amp to your stock deck it is possible you will have to get what is called a line out converter which you can find at circuit city for about 30 bucks this will then create two rca outputs for you to plug in the rca's from your amp into.