I cut a couple of half circles out of styrofoam to make something almost identical to what's sold in this kit:
Neck Gasket Repair Tool Kit
Used lotsa el cheapo clamps from harbor freight, aquaseal and attached new gasket to the old one and it turned out great (ie, it does'nt leak). The process in the video is way more elaborate.
The problem with having a shop do it is'nt the cost, $25 labor is'nt bad for the amount of time it takes, its not having your drytop during peak paddling season for however long it takes for them to get to it. If you do it yourself its ready the next day. I also wish there were a cheaper source for gaskets, $30 for the rubber gasket seems kinda steep...