Ride Length: As other people have mentioned, it's going to be about an average length for a roller coaster, maybe longer (3-4 mins, if I remember correctly?). Most of the time is spent going up to and travelling up the lift hill, but that's true with any standard coaster.
Remember that the ride will be stopping at several locations for show scenes. I think the train stops once at a base camp near the top of the mountain to change from forward to reverse. Of course, it has to stop once more to turn forward again. It will probably stop again for the Yeti, likely followed by a launch of some sort. There's a decent amount of track in that pile of steel.
Number of Trains: Realistically, they will probably run 4 trains at a time. In an ideal (ie unrealistic) situation, they could probably run 6 given the number of blocks that are on the track. It's too bad the station isn't dual load.
Maintainence Bay: With most coasters, the maintainence bay is right next to the station, typically running parallel to the final break run. As ogryn suggested, that area behind the retaining wall might be a good place for it. They could easily put a switch track between the station and the first mini-lift (this is how The Barnstormer is configured)