Lots of good advice on this thread. If you end up thinking that the bike doesn't fit properly, you can find another and sell this. The process of learning how to work on this bike will be helpful on your next bike if you do sell it and keeping this running properly if you don't. This is a really good bike to learn basic bicycle repair skills since the parts are bog standard and readily available.

Basic idea is to do a complete overhaul (grease does not get better with age) and replace all the consumables (chain, cables, ball bearings, etc.). You'll likely want to change out the tires and brake pads as well (try kool stop pads). At that point you'll have a bike in tip top mechanical condition.