I'd buy it from some nice Canadian guys before the chinese, fwiw
You can get 2 of them from Cnn for cheaper than the price from Horizon...ohh well, I guess you gotta do what you gotta do
As far as replacing the trackball on the bold, you pop off the trim ring around the trackball and just pop the assembly out by tapping the back of the phone. Its held by a magnet. Also, the Bold is really easy to assemble and disassemble. There is a video on how to do it if you would like to search for it...the guys at CNN did it and it was posted on this forum