I agree with Steve. I'd like to add that how long it takes to
understand any scheduling software is greatly influenced by how much
experience you already have in scheduling, particularly critical path
scheduling, and in Project Management. If you already know these
things, it's just learning how to apply these concepts in a new tool.
The same idea would apply to learning Excel - if you already know math,
i.e., the order of operations, it's much faster and easier to learn
Excel.
If you want to be an expert in Project, use it to schedule a few decent
sized projects and learn not only how to schedule, but how the schedule
affects and is affected by other considerations, such as Quality, Risk,
Communications, Earned Value, etc. Just like most tools, in isolation,
it appears much simpler than it is in the "real world", where it is
interconnected with other factors.
As far as MSP trainers - most of them that I have met have absolutely
no concept of how this tool is applied. They teach "push button"
classes, as Steve said, and leave the students with no real
understanding of how to make this work on real world projects.
The best way I've found to tell if they really know how to apply MSP is
to ask if they know what "feature" must be turned off to use Project
effectively. If they don't know that, they don't know Project.