Hello crash,
This is a common problem on these cars.The reg is easy to replace. Drill out the rivets and replace the part with new m-b rivets, will need a large rivet gun, the part is around 100 dollars.
It comes with or with out the motor. no need for a new motor. The best way to avoid this happening on the other windows is to open and close them every few weeks. If you look you will see that most likely one of the plastic wheels broke.
Fastlane has the parts for less than 100. Dan