My experience is that the walk is 3-5 minutes depending upon your room location in the Garden Wing to the Tower building. The walk is not enclosed but there is a covered walk between the two buildings. Also, you need to take the escalator / elevator up to the 4th floor of the Contemporary and then take a second escalator / elevator to the monorail platform. I would budget an extra 2-3 minutes for the escalator / elevators.
The ride from the CR to TTC is only a couple of minutes. The ride from TTC to EP is about 15 minutes. But, you do need to exit the monorail at the TTC, walk down to the base-level of the TTC, and then walk up a ramp to the EP line. That will take you 5 minutes or less.
Accordingly I would budget a minimum of 33 minutes: 17-20 minutes for monorail time, 5-8 minutes walking at CR, 3-5 minutes walking at TTC. Plus, I have not accounted for time waiting at the monorail platforms (which I cannot really speculate because I don't know how quickly things are running and when you arrive at a platform).
As an aside, I love CR (it's a great spot) and the monorail is just so whimsical.