Removing the shaft is obviously pretty easy. (2) 14mm open end wrenches and a bit of elbow grease, and it's done.
As far as welding up the new shaft, I'd make yourself a jig to ensure that the shaft stays good and straight. I've seen a few people weld up a shaft, which has a slight bow to it, and the shaft wobbles it's way to an early death. Not to mention killing the U-joints off during their teenage years. Not much fun being bound up, giving a little skinny pedal, and hearing that front shaft give the scream of death as it comes apart.
I wouldn't worry too much about balancing the front shaft unless you drive in the snow and keep the front end locked in at higher speeds (20mph +). If you plan on doing that, it'd be worth the $150 to have a shop weld it up right for you, and balance it at the same time.
Erik
