I do my seals all the time. It is super easy and changing a neck seal takes less than 30 minutes from start to finish and that is on a crushed neoprene suit (Trilams are much easier). I consider a neck seal harder than wrist or ankle seals. A heat gun will have the seal off in about a minute, then a little prep wipe with MEK and you are ready to glue the seal back down. We use PB300 for glue, and do not clean off all the old glue prior to re installation.
Zippers are best purchased from GLobal drysuits due to pricing, but I have found the OS seals to have a better fit. I've also become a believer in the seal protectors beyond straight silicon. Look at OS Systems website and find the seals and glue. Near the top of the webpage it also says "maintenance and repair" where there are instructions on how to perform the repairs. http://www.ossystems.com/