I used to have that exact kegerator (badged as a Sanyo, and clad all in black, but the same internals). I've gotten 3 ball lock kegs into it at once, with the CO2 inside (note -- you need a 3" diameter tower or larger if you want multiple taps).
As for what you need, you've got it pretty well figured out. New lines is a must, since you don't know where it's been, and it certainly needs a good cleaning. But here are the basics:
1) New lines. 3/16" beverage tubing (buy 10' up front, since it's cheap; you can cut it down later if necessary). 5/16" air line.
2) If you plan to serve commercial beer (i.e. standard American Sanke taps), you have everything you need.
3) If you want to serve homebrew, you need a corny keg, and then the associated quick disconnects for either ball lock or pin lock kegs (whichever you end up with -- ball lock are more common). You then need adapters for your lines to connect to the quick disconnects. If you go ball lock, just buy
this and
this.
Other than that, you're good to go. This is quite a score!