Re-regulation would be required if the barrels are fixed/soldered. Regulation is one of the main costs of a non engraved DR.

Alan Moon in NE did his own regulation, resoldering, so it's not impossible for the expert non professional.

If a self adjusted set of non fixed barrels, just adjust the wedges yourself, if the rechambering is safe.

There was a Pedérsoli hammer dr in .45/70 which was rechambered to .450 No. 2 NE. It was sold and resold again and again, multiple times. Why?