Newbie looking at an 83 13B -- risky?

[JonnyVon]

I've been watching Craigslist for some time now waiting for a good RX-7 to come up (and saving up meanwhiles), and I found one locally that's going for $650 minimum:

http://omaha.craigslist.org/cto/1028558495.html

I haven't seen it in person so I don't know the extent of the body damage (obviously rust needs work, dents need to be hammered out or the panels replaced), nor the mechanical condition. But, would the aftermarket modifications be any cause for concern, at least in terms of extra maintenance charges incurred? (I do intend to learn how to fix things up myself, at least as far as it's practical.) Also, any particular trouble spots from that model year to look out for?

Finally, my basic question is, would spending $650 on this car, and then tacking on parts and labor I can't do myself, run me more overall than it would to save up $2000 or $3000 and go for an RX-7 of a similar year in better shape?

Apologies if I'm overlooking anything glaringly obvious, it'll be my first foray into rotaries, and I haven't been lurking the forums for long.