Ain't no bass in the Quabbin. Seriously, though, the quality of smallie fishing at Q has been on the decline for the last three or four years. There are still plenty of fish, but the days of 40-50 2+ lb smallies are gone. Part of it is the increased bass fishing pressure as well as meat fishermen who pull them off their beds and keep them. Another problem is the slot limit for lakers that resulted in a huge population increase of medium sized fish. I've actually seen lakers preying on smallie beds in the spring. The baitfish populations have suffered as well. Five or six years ago, you couldn't help but catch a bunch of rockbass, now they are almost nonexistent.
As far as maps, many of the local stores (such as the New Salem General Store) sell a reasonably decent map, but there is no substitute for time on the water. The water levels fluctuate greatly, and if you run around at full speed without knowing what's below you, you will lose a lower unit or worse.