What you describe in your initial post sounds like an early model mountain bike, possibly from the mid '80s. Taking it to a bike shop is a good idea, because they can tell you whether it's worth investing any time, effort and money. A quality bike from that era might be; a department store bike, probably not.
A basic workover--new chain, tires, tubes, rim strips, bar grips or tape, cables, brake pads; repacked bearings; trued wheels--will probably cost a couple hundred bucks unless you're a DIY kinda guy. Parts and tools will cost perhaps half that. But, it will completely transfrom the bike.
What I hazily recall from Boston is awful roads and awful traffic. Unless that's changed, I'd stick with a mountain bike with street tires, a commuter bike or a cyclocross bike. You want strong wheels, tires suited to wet pavement and some kind of suspension--at least the fork. I'd avoid a classic roadrace type bike.
I'm bike-commuting about 20 miles RT these days and use a mountain bike. Works great, especially with eighty pounds pressure in the tires :-)