Hey Fissel,
Yes, it's actually Very simple.....
I hooked up my Alpine V6(? I think!!) to my deck, I'm running one 10" and one 8" under my rear seats. Sounds great. I like the sleep look of the factory too.
Rather than using the RCA outs, most amps have an attachment, I can't remember what it's called, its a little square plug (I can't remember for the life of me what it is called....but this is what you use when you aren't using RCA's) in on the amp, the male attachment just has a L + - and R + - wires...so 4 wires in all, you plug that into the amp, and wire the L + / - to your Left side front or rear speaker, likewise with the right side. I did all of this right from the back of the Headunit, I found diagrams online of the Ford Factory Stereo Wiring for the Sport Trac, next, power your amp to the battery, and ground wire from amp to ground on truck, then use your remote wire to attach to the power unit on the stereo...that way the amp goes on/off with the stereo power. I think that was everything I did. I've done this before on my Cavalier, so this only took me an hour to do. It's very simple, just use your due diligence and do a lot of online research, its all online.
So to answer your question...YES. It's Simple to do, and costs nothing except for the wires involved. You don't have to buy any special attachments. email me if you have more questions, I'll see if I have any of my papers laying around anywhere, so I can give u a bit better direction.
If your Amp DOESN"T have the plug-in that I'm talking about, then the only other way to do it is how Andy said a few posts above. Next time I'm in my truck, I'll check what its called.