1) 2-4 years (but at least 2 years). Back in the day, BYU used to let guys count their mission experience as work experience, but that is no longer the case for most people (IMHO, a good move by BYU.) A lot of the value in your MBA experience comes from bringing professional perspective into the classroom discussions and projects that you work on. Plus, if you expect to get decent offers after you graduate, you'd better have some solid work experience on your resume. Recruiters don't care that you were assistant manager of the Dairy Queen when you were in college, or that you were an AP on your mission.

2) I would start with a prep book and would take a couple of practice tests. The key is learning strategies for how to maximize your GMAT test taking ability--not necessarily learning new material. The math is algebra, geometry and numerical properties--stuff you should have covered by the 9th grade.

3) I don't know--I didn't live in Utah County when I took the GMAT.