Jack,
First of all welcome to the site, you have stumbled upon a vast warehouse of expericence and knowledge and there is not one person on this site that will not go out of their way to help you.
First of all go out and buy yourself the best helment you can possible afford DO NOT SKIMP ON THIS point.
Second everyone would suggest you get the MSC out of the way first.
When it comes to Triumph's this may sound weird but you are about to enter into a life time love affair with your bike. Triumph loyalty runs deep. I would safely say that many of these guys on this site would walk if all the Triumph's disappeared tomorrow, before they rode any other type of bike.
The thing about Triumph's and this really going to sound weird is YOUR bike will talk to you, what I mean is you can be standing in a room with 100 brand new speedies and america's and one of them will talk to you, believe me you will know when you find your bike.
As for the various models, I own a America it suits me and what I want it to do perfectly, round town, 2 up and long tours. Do not let anyone tell you these bikes are under powered I have yet had anyone run away from me in fact it seems they are trying to catch you.
Once you find your bike, you are going to want to tinker with it and everything you can possible do to a Triumph you will find detailed step by step instructions here. If your not sure about something STOP and post what you are doing and what you want to do have a beer and the check your post and and you will have your answer in about fifteen minutes.
Remember this is a global site and sometimes it can get a little heated in the general forums area, we are ALL TRIUMPH owners and we all have that in common and everthing else takes a backseat when it comes to our bikes.
Again good luck and welcome to the mad house.