330d also came with 6spd manuals. I have one. General consensus is to steer clear of the autos. On the diesel they're more prone to fail, but if you nurse the car and resell after a year or so it doesn't really matter. You're going to struggle to find any 6 spd manual E46's worth buying.
Auto's are everywhere and 5spd only. If you can find a 5 speed manual 330d that's probably your best bet bang for buck.