Acad VBA Book

I would highly recommend anything by Joe Sutphin. I have one of his and find it to be a great reference with excellent examples. His example code snippets are some of the best I've seen. He leaves the samples to handle what he's trying to get across and doesn't clog them fancy code.
Yes, and yes. I've found VB to be extremely helpful due to it's vast uses. I learned VBA starting with Acad, but have now used it successfully with office apps as well as VBScript with ASP web pages.
Learn lisp as well if you're going to be concentrated with Acad. There are things lisp will do that simply aren't handled well with VBA.