Recovering seat, how difficult?

[dbozman]

The seats in my '74 are shot, but the frames are good and the foam is OK. I like the look and feel of the stock seats and would rather use them than aftermarket.

I was looking at this "custom-fit" set for a little over $300:

http://www.1aauto.com/1A/SeatUpholstery/Chevrolet/BlazerFullSize/1AISU00035/148623

Anyone ever done this? How difficult to do it correctly? Thanks.
d