I would not trust just any garage to do a BMW engine swap. There must be 3 or 4 highly knowledgeable BMW indy garages in New Hampshire. I know of one in Albany, just outside of North Conway. Two weeks ago while on vacation near Mt Washington, I dropped in to say hello to them. Owner is Mike.
I also always recommend joining BMWCCA.
https://wmc-bmwcca.org/