I'm a bit rusty on mastercam now, but having used both that and edgecam I'd say it's a lot easier to pick up mastercam from scratch. The help files, in contrast to edgecam's obtuse efforts, is absoluetly first class. It's an extremely easy program to use and you'll pick it up no problem.
Posts are probably the opposite. Edgecam is excellent for creating posts and, while I'm sure it's improved, it's a bit labourious in mastercam.
Obviously, as they are both CAM progs, there is a bit of overlap but you're best bet is to treat mastercam as an entirely new program as there is significant differences in their respective approach. If I was you I'd, ahem, 'aquire' (cough, nudge) a copy of mastercam from the dark side of the internet and have a play with it at home.