If you can get the padding for the seats, it's an easy do-it-yourself install. Just follow the directions. It's basically a matter of taking the covers off, putting the new padding on the springs, and using hog-rings to attach the covers to the seats. It works easier if the materials are warm, so leave it all out in the sun for a while then do it.
My dad has done this on a 56 Chevy and a 68 LeMans, I'll ask him what company he got the materials from and get back to you.