Are you just asking about the cost to frame the opening and hang the door, or are you wondering about the whole project, i.e. removing the old door, framing in and drywalling the unwanted hole, patching the baseboard back together, etc.? Do you hope to reuse the old door? Where do you live?

I can take care of removing the door and closing up the existing door hole.

Just need someone to remove the drywall where the new door will go, cut out the studs, frame in the opening and hang the door. If possible, I would like to reuse the existing door as its the right size and matches all the other doors. I can take care of the baseboards and trim.

I live in the midwest.

Sounds like it would take a day, or maybe a bit more; a few hundred bucks would probably do it. So much depends on the local market, the particular handyman you find and peculiarities of the existing framing. Don't forget to consider the flooring, which may complicate things.

If you're comfortable removing the old door jambs, closing the hole and trimming everything out, I'm surprised you don't just frame the new opening yourself.

I have thought of just doing the entire job, but I haven't ever framed and installed a door. The other stuff I've done quite a bit.

So... How did it turn out? :)