Wilsons Sandbox

Hey- I need to replace my valve seals. They were replaced last winter by my local dealer while they were cleaning up my head (long story), and now are leaking like crazy. I would rather do it myself than give them a chance to try again. I have read a few things online about using aftermarket seals for a KZ 1000 Police bike as they apparently last longer than the new KLR seals. Anybody done this? Can it be done without removing the head? What is the best way to depress the springs and remove/install the keepers? Any other tips on doing the job? Thanks, Matthew