I sold my 79 a couple of years ago. Here are a few things to look for, and be wary of:
If you haven't driven one, you're in for a surprise when you try to shift it. The throw from 1st to 2nd and 3d to 4th is about 12 miles. A short shift kit will help, but its still a longish throw AND it will be much more difficult to engage the gears with the short shifter.
Look closely around the door striker plate and on the door sill for rust. Unless its been fixed, there more than likely will be some, and you need to look further to see how much there is. This could be a safety issue if its gotten very far.
As was said below, it's gonna leak. Put cat litter on the floor under the engine and forget about it. The oil lines running to the front coolers tend to leak. IIRC, they're around $200 or so for the lines. When the clutch starts to slip (and it will, especially on a car with 130K miles on it) you can start attacking the oil line fittings, gaskets etc etc. while the engine is out.
I found that most parts for it aren't THAT expensive. There are tons of parts available for almost every system on the car. Shop around and you can find pretty good deals on them.
The ac sucks majorly. Even with the new rotary compressor it still sucks. And plan on topping off the freon yearly, or bi annually at least. The condenser for the ac is mounted to the engine cover (on the 79 anyway). Mine developed leaks in the lines to the compressor from the opening/closing of the "bonnet" , among other places (actually that's not bad for rubber lines that are over 25 years old)
On the good side. It WAS fun to drive. The repairs, if you diy, aren't too bad. And, as was said below, it was pretty photogenic. Unfortunately, all the pics of the 79 are on the other computer.. the one with the virus that can't be cured. damm
As was also said below, buy the best one you can find, same as the advise for buying a Boxster. Get a PPI done by someone who knows air cooled engines. Have fun with it!
Bob