If you need to replace the seatbelt with your good working part, it removes and then installs with just one bolt.

Note that when re-installing a seat belt buckle the bolt should be secured with a dab of blue thread locker to ensure it doesn't back out.

The process shown here of removing and replacing trim and your seat belt can be utilized to install a passenger seat as your driver's side seat as well, for example. The seats are the same for either side, and have mounting holes on each side for the different trim pieces.