The part is actually called the reaction sun shell. It is a known weakness in these transmissions. It's failure causes a loss of reverse, 2nd, and 4th gears. Due to it's location in the transmission, the transmission must be disassembled to replace it. Most people spend between $1800 - $2500 to have their transmissions removed, rebuilt, and reinstalled. $1265 is a decent price to have a remanufactured unit installed. Just make sure that it has the recommended upgrades, such as the stronger sun shell, and the redesigned valve body.
For more information and pictures check out this thread:
http://www.automotiveforums.com/vbul...d.php?t=461182