One thing I can offer in response to your questions.
If you have two choices and you want to see what they do then try them. I would say that most people who use computers a lot and are known as experts got that way by trying things. If you try something and still can't figure out what it does then you should try to read the manual. That way the simple stuff will come to you without a lot of reading. You will no doubt learn something along the way.
To really get a grip on how dialup works you need to get into the command line and setup a connection that way. Following a howto like this one will teach you more about what's going on than you'll ever get from the GUI your using.
http://www.linux.org/docs/ldp/howto/PPP-HOWTO/
It may seem like a lot to go through to get online but if your wanting to learn something it's the price you have to pay. Once you've gone through setting up a connection using pppd and chat from the command line using any GUI should become trivial.
