Any upholstery shop can cut the heaters out of your current seats and sew them into the new.
Here at our shop, we are not upholstery guys, but we' have been swapping upholstery from seat to seat. (for instance when we have power seats with nice upholstery and need them in a car that isn't equipped for power seats, so we swap them onto manual seat frames. Its a lot of work but entirely do able by a DIYer. Meaning you could do most of the removal and reinstallation, and drop it off at upholstery shop for them to sew it in.
If you attempt this start on passenger seat with bad upholstery, so if you jack it up who cares, then cut the heaters out, then take apart the other seat Use the airbags from original car or at least make sure you match part numbers on the airbag because it there are year differences that will not work.
Sewing the heater in yourself?
Most upholstery shops us a "walking foot" type sewing machine to make evenly spaced stitching for when its view able. Since sewing the heater in is happening inside the seat and not view able you might be able to get by by sewing it in by hand. Might or might not be able to use a "common" sewing machine to sew in the heaters. I actually think you could because its not view able and evenly spaced "pretty" stitching isn't critical.