For obvious safety reasons there are no possible repairs to the seat belt retractors. If they are not functioning correctly they need to be replaced.
NOTE: The torque prevailing nut used to secure the lower seat belt anchor is not reusable. Verify availability prior to proceeding.
CAUTION: Do not reuse the bolts attaching the seat belt retractor to the seat frame.
Normal hand tools is all you need with the exception of Torx bit sockets. You will likely need a set of these.
Replacing the retractor requires a certain "mechanical ability" and knowledge but isn't rocket science. If you are going to attempt this just take your time.
Technician
22 Year Factory Trained and Certified