You can get the wiring harness adapter from any auto parts store. You'll need to either crimp or solder the wires from the adapter to the stereo harness. You'll likely need an antenna adapter as well, since the antenna plug will not match the one on the new stereo. And finally you will need an adapter to hold the stereo in place in your car's dashboard.

As for the deck you want, $100 shipped is a good deal. You wont find many reliable aftermarket am/fm/cd decks for less than that.

If you want help assembling any of this, let me know. I've done tons of em.