I had a kokatat drysuit and replaced the failed ankle gaskets with latex socks myself. I watched a lot of different videos before starting. I don’t believe the gaskets were stitched onto my suit. Don’t know if NRS stitches theirs. Some of the videos and instructions state that as long as the latex is still in good shape where it attaches to the suit (pliable and w/o damage), you can just cut the old gasket off to the edge of the fabric material and glue to the latex. Mine were old and crumbling, so I had to scrape it off using a knife.
The hard part is making a form that will fit up inside the leg, that will stay in place while your gluing the sock and taping it so it doesn’t move, and that you can pull out from the inside of the suit through the leg and the outer cuff that protects the gasket while you’re wearing it. At first I was considering a large chinese soup container, but fortunately I tested before gluing, and realized that once glued up, I’d have cut the container up to get it out. I ended up using some chunks of gray packing crate foam from work to make the forms.
Next time I need a gasket replaced, I’m sending it off. I know I can do it, but it’s a PITA, and worth the charges to me. I just didn’t want to wait for the shipping round trip. And after all that, it was an old suit I hadn’t used in years, and after replacing gaskets, I discovered most of the seams leaked. Ended up having to buy a new suit, as they were deemed unrepairable by Kokatat.