What happens in the brain and the body when ACh levels are elevated?
For instance, what processes does ACh regulate?
And does it have a secondary mechanism?
Does it elevate/lower hormones or other neurotransmitters?

Depends on how you increase ACh (choline precursor, AChEI, etc) and to what degree.

This link should answer some of your more basic questions:

http://en.wikipedia.org/wiki/Acetylcholine