Think it might be better to have it done in the winter? My local dealer is swamped spring/summer and dead in the winter.
Would I be more likely to get an accurate valve check if they didn't have a a bunch of service orders stacked up, or do you think it doesn't matter?
Talk to the owner of the dealership, or the guy that runs the shop. I'm sure they would prefer you bring it in when they are slowest. They may even work with you on price if you ask them nicely. Most shops have some type of winter toy maintenance going on, but nothing like spring, summer, and fall. I would expect you'll get a better job if they are not in a rush.
Doing the valves on the C14 requires a lot of space for all the parts that have to come off. That's another reason to have it done when they are slow, less chance of things getting kicked around.