basmith - Never had to replace a head. I think it depends on where it broke. It the shaft broke, then you can replace the shaft, if a part of the head broke, I think you're SOL.
In regards to purchasing a Driver, I wouldn't buy one. I have used my driver maybe 4 times in the past 3 or 4 years. I always tee off with my 3 wood. I have a slow swing (and a terrible slice) so my 3 wood is better for me. It's heavier than a driver so my ball tends to go further, and straighter. This just works for me though, it's probably different for everyone. Also remember, a bad day on the course, is better than any day at work
ENJOY!