Evan, you should be fine with the system above, it is the same one that I have. The last item you are referring to is a mobile decoder for a locomotive. You would use that to upgrade an engine from DC to DCC. If you plan on buying locos w/DCC already installed then all you will have to do is select loco 3 and your good to go.
Of course to separately control each engine you will have to program them to different addresses, but don't worry, you'll get the hang of that after you get your system up and running.
Of course to separately control each engine you will have to program them to different addresses, but don't worry, you'll get the hang of that after you get your system up and running.