If you get the correct seat cover, it's too easy, at least on my 89. The original seat cover has plastic channels that just snap on over metal pieces in the seat. Of course I went cheap and got a universal cover off ebay, and had to rig mine with hog rings, but if the covers are set up original, it should be a breeze to install. LMC Truck sells covers, and possibly someone on here could verify if they have the original snap on design, and if all years had this design.
If you order from automotiveinteriors.com you get an excellent quality kit to completly replace the old cover. You remove the old cover and pull on the new cover and use the hog ring kit to fasten the new cover to the frame - it's easy - mine fit perfect and you get more than enough hog rings to fasten it tight.
I was looking at the one on my 84, and it has the plastic snap on seat cover. If you find the snap on cover let me know. How much did you give for yours Franklin2? Still debateing on recovering it, or using some left over 89 Mustang GT seats.
I found a deal on ebay, a guy had some surplus for about $30.00. It was not the original pattern, and was a universal type, but it fit fine, though like I said it required I add some wire for the hog rings to fit. It's not original, but a lot better than a slip on and tie seat cover.
There's an upholstry shop we use sometimes that'll do bench seats for $100, I might try them if i cant find anything on ebay. I dont care if it's original pattern or not, it's just gonna be a weekend cruise truck.