all good questions and been there
to start apache, it is on your machine already, just go to the system preference panel, then to sharing, and select web sharing then click the start button
Mac is pretty good at the security thing (think Unix). Mac hides about everything so you can't screw with it even if your signed in as root. In an earlier version of 4 I was able to find the files I wanted to screw with but can't figure it out now. So, I go through the Terminal now. Still not a master by any means, but am working on it.
Some good lessons are at (and I'm sorry if I sound repetitive here with my other posts) but, lynda.com has some fantastic videos, free samples, that you can watch which can teach you alot about the Mac and its Terminal when it comes to dealing with apache, php etc. Jump over to her site, go down the list to php and select the first one. It will take you to a page that has general info to installing, for free. There are quite a few so expect to spend some time there. I'd say it is a must see if your just learning.
Also, you will fare well to make a trip to the library and pick up a book on Mac OS X 5 - dealing with Darwin takes a bit.
And of course, if you find out how to access the files without going into the Terminal, let us all know.
To make it easy, just load XAMPP, all the files you will need to access will be reachable without the terminal. Still, read up on it.