I feel for ya -- Just went through similar for an intake manifold/plenum I did NOT want to remove lol.
You would need to know if the seat is OK and how much meat is left for threads to choose a method.
All of the links I saved below:
Good Seat (Precise drilling is required!):
repair-kit-for-1-4-in-to-7-16-in-or-7mm-to-10mm-screws
repair-kit-for-5-16-in-8mm-and-larger-bleeder-screws (Tap to 1/4 NPT)
(Check seat angles!)
Bad Seat
brake-bleed-valve-kits (Very Expensive)
bleeder-screw-repair-kit - (Tap to SAE 7/16-20 Instructions) Best bet if you have enough material left, imo.