Gas is not something to be taken lightly. Many areas require a license to do gas work. There are also insurance issues. You cannot put a price on you or your families safety.
I know a guy who piped up his own gas line with SharkBite fittings.
Wouldn't recommend it.
Unless your handyman is confident in his ability and you're inclined to believe him, you're better off with someone trained in it, and as has been said, it may be a requirement depending on your area.
Is this really even a consideration? Would you let a general physician do surgery on you or would you get a specialist? Handymen are cheaper because they generally don't take the necessary steps and materials to do the job properly in the first place.
Right after safety, the main concern would be your Home Owners insurance company. If it isn't installed to code and with proper permits, they can refuse payment if something goes wrong.