Balance

So, it's time to change the pastey bb on my mtb, but we can't get the darned thing out. Went so far as to put the whole bike up in a vice, squeezing the bb remover and trying to turn the bike. No good. I've heard that some people heat the bb shell to get accomplish this, but wouldn't that melt the paint? Also, I'm thinking i want to replace it with an oldschool non sealed bb because it would be a lot cheaper (free used parts) and much easier to service. I don't mind working on my bike, so the seals are just something to damage. But I'm not sure if I can install that type of bb. It would likely be a road bb, and because my mtb is a bit older, the bb shell isn't overly oversized. Has anyone done this before?