If a 2000 Elantra airbags are deployed and seat belts are locked how do you replace the seatbelts and will the seatbelts work if airbag light is still on?

Replacing the seatbelts involves removing several interior trim panels, unfortunately almost all of them, starting from the front. If the seatbelt will no longer retract, it is non-functioning and needs replacement. Seat belts should ALWAYS be replaced after an accident involving airbag deployment. The airbag light is telling you the dealer or a qualified mechanic needs to do some slightly dangerous work replacing the airbags and the airbag controller.