I did my own and not that hard.
1) pull your seat off, use a silver sharpie to mark some locations where the cover meets the bottom of the pan. Pull the staples and pull back, if you have a pillow top you have some plastic washers and strings with metal tabs. push down on the top , turn the tabs and slide back through. Save the washers for reassembly.
2) take the gel pad and put it where you sit. You want to cut a wedge out of the back about 3" wide by 3" deep. and discard. Mark it with a sharpie .
3) take a razor knife adjusted to the depth of the gel pad and cut down on the seat foam on the line you made. Now make some cuts the same depth about an inch inside that cut. Pulling the foam to the side undercut the foam. repeat until your gel pad sits inside, there will be a void where your back wedge was cut out.
4) take an aggressive file and narrow the front right and left sides of the saddle where your legs go down and reshape those.
5) with the gel pad in place , cut a wedge of the memory foam to fill the wedge, ok if it's thinner than gel. Cover the top with the memory foam. Make slits where strings go through pillow top and gel.
6) pull the string back through the top, a tire plug tool can help here if you push it from the pan to top make sure you have the washer in it. Turn the metal tab across the washer and go to next.
7) match up your marks for the cover and re-staple the cover to the pan with 1/2" stainless steel staples
Items needed, silver sharpie
1/2 stainless steel staples
gel pad
1/2" or 1" thick memory foam ( at walmart, kmart... you can find a seat with gel pad and memory foam for a chair usually about $20.00) you can pull that apart.