Removing OEM seat covers

How hard is it to remove these and reinstall them?

I am looking to do the center of my seats with the same fabric as my door panels, how hard is it to remove the OEM seat covers so I can machine sew this fabric in and re-install them?

The covers are 2 pieces, the back of the seat and the bottom of the seat. You can cut them apart, but if your having to ask how hard is it to remove them, your going to ask even more on how to fabricate the center pieces, and put them back together correctly.

It would probably look better if you took it to an upholstery shop and had it done.