The last one that I took apart that had a considerable amount of play in it had extensive wear on the the sector gears and the ball nut. Those parts don't come in the kits. Also the worm shaft actually serves as the inner bearing race on both ends. If it is pitted new bearings won't help much.
ABS in Orange, CA is a good place to have them rebuilt. Probably about the same cost as you stated.
Fred
