$125 and hour may be a little steep, but that all is market/region dependent. Sure, you can rush through installing in-ceiling speakers, but it's best to at least figure 30 minutes a speaker to make sure everything is done properly. So figure 2 hours in labor for the 4 speakers alone, another hour or two for the speaker wire, then termination, cleanup, etc. From an estimating standpoint you're looking at a day's labor.
From the C4 standpoint the most important thing he (your dealer) needs to be aware of is your network. If you've got a solid and reliable network, setting up a single room with an EA-3 (or EA-1), with the equipment you listed, isn't going to take a whole lot of time.
At the end of the day, you've got a room with a Kaleidescape system and some nice equipment, so don't short change the room on control or the Atmos install.