Seems to me that if the carpenter you have knows anything, then he can do the job--if you are sticking to the original size opening, then all he needs to do is put in new jack studs and a sill for the door, then hang it. With this method, you use a masonry saw to cut vertical lines through the brick at the bottom of the window, no need to do more masonry than touching up the mortar joints.

If you are widening the opening, then you get into replacing the header, installing new jack studs and possibly king studs, and a whole lot more masonry work to neaten the edges of the new opening...the plus is that the waste brick can be reused to do the masonry repairs in both cases.

I've done a number of these--windows to doors, including sliding double doors. They're never as simple as you think. The saw cuts usually end up leaving some bits and pieces of masonry that have to be patched or covered with trim. But nothing more than a competent real carpenter/handyperson can handle. Keep in mind that there may be wiring in the wall that you're removing that has to be rerouted. And once you remove the wall section, there will be voids revealed that can cause drafts unless they're sealed and covered.

Talk to your carpenter about whether he can do the job. If not, then ask him for referrals to someone who can.