I replaced my neck and wrist seals a couple of months ago on my drysuit. I removed the old seals. I found the easiest way to do it was with a hair dryer set on low to remove the old seal. You need to be very careful not to burn the suit however (lowest heat setting, hair dryer about 1 ft away, directed to the seal for a couple of seconds max, remove a bit of seal, and repeat). removing the seal took far longer than replacing the seals. Alternatively, you can glue on top of the old seals. I think the wrist seals took me about an hour and half, the neck an hour and 15 or so. And I've seen shoddier professional jobs