I've done this several times before using a hammer, carefully selected sockets, some snap ring pliers and nothing else. Just be careful and take your time drifting the bearing cups in and out. Soak it well in advance with some penetrating oil. Clean impeccably while apart to ensure the new cups go in nicely. If you do it right (hard to explain, sort of like a puzzle) you never have to rely on those needle bearings staying in place as you drift the bearing into place. It shouldn't need rebalancing afterwards - you can't get the u-joint in uncentered unless there is something wrong with it, and as long as you put the yoke back onto the shaft in the same orientation (i.e. mark it before disassembling) nothing should change with the balance.