Drysuits are great at keeping you dry and warm even water the water is in the low 30s and it's a breeze on day in the Laser. That is until you get careless one day pulling it on or the years just get to it and one of the seals breaks.
Replacing the seals on a drysuit is pretty straightforward, you just need the proper materials and a little bit of know-how. I had to replace the wrist seal on my suit so I put together a video showing the steps for replacing a seal. The same technique works for any of the seals - for the neck I sometimes set it flat and put a book on top, but a large round surface like a basketball can work as well.
The materials you'll need are Aquaseal, Cotol and replacement seals along with the gloves and something to hold the suit apart. Remember to work in a well ventilated space.
Remember to stretch out the new seal by leaving something in it overnight (like a can or full soda bottle). After stretching it may still be too tight, in which case you can carefully cut it along the ridges inside the seal. The seal does not need to be super tight, it really just needs to make solid contact all the way around. There's no reason to spend the day suffocating yourself, just be careful when cutting and remove only one ring at a time testing for fit in between.