Brendon, the answer to all of your questions are: It Depends...

It depends on what you want to do, what you have (or can afford) to do it with, and what do know how to do. For the best background reading, try this link to[link=http://www.rcgroups.com/forums/showthread.php?t=84771]Mirco Thread Index[/link]. It has explanations of most of the questions you could ask, plans for a number of models, links to all sorts of resourses. It covers everything from making 'Bit' car conversions (the little zip-zap R/C cars) to winding your own brushless motors...