That's a good price for an R75. Be skeptical about the mileage though. It could be anywhere from 160k to periods of broken speedo. 1st, get a Haynes or Clymer manual or even both. 2d, read up on what SnowBum has to say. 3rd, run a compression and a leak down test. Be prepared to replace the coils and points. Nothing wrong with running points, it's a good system, but may need some tuneup. The spline lube isn't difficult, just time consuming the first time you do it. No shortcuts, remove the tranny and inspect the seals and splines. 4th, you're going to need a lot of rubber bits. Hucky's spare parts is a great source for older airhead spares.
Or, you could just change the fluids and ride the heck out of it this season and then do all the work it will need over the next winter!
Airheads Rule!! [smiley=beerchug.gif]