Yes, you should be able to do this without pulling the engine or any body parts.
Only other thing will be accessing the cable housing inside the passenger compartment. The stock cable has one fitting at the lever end, and it splits to run back to the two heater boxxes.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)