That sounds like a pretty good price to me. I recently sold a 2006 Revolution for $1000 in good condition. Those 2001 to 2003 Drives are very strong, and the first generation Mirage Tandem (later named Oasis) is a great first boat! If anything happens to the boat, the Drives alone would bring $700 to $800 in good condition.
True, the 2009 and newer boats are stronger and have a few more features, but if the boat is solid, it sounds like a lot of bang for the buck!
You can upgrade those original drives to ST or Turbofins. Turbos will put a strain on the boat if you run them hard, but the STs would be less likely to cause any problems (and do not require you to purchase new masts (rods). Then again, the original fins work fine, just not as efficient as the STs.
We had a 2001 model for several years and had no problems with it -- it was a fun boat! The stability is very good, it cruises along very nicely and you can solo with counterweights in the bow, making it quite versatile. As I recall, it didn't have a sailing capability that early, if that matters. You can double check with the seller.
PS: The Oasis (now in its 4th generation) is the oldest continuing Mirage Drive kayak. It was obviously a great design from the outset!