1) Yes, 9mm Luger is the same thing as 9mm. You will also see it referred to as 9x19mm and 9mm Parabellum.
However, there is also 9x18mm (aka 9mm Makarov), and (although I doubt you will ever run into cases marked as such) 9x17mm (aka 9mm Kurz, & .380 ACP). These are
NOT the same 9mm used in the Glock 17. Just go to whereever you buy ammo and ask for 9mm, they will know what you are talking about.
2) 9mm +P is a hot-loaded 9mm (More powder = more power, kick, and wear on your gun) and 9mm +P+ is loaded even hotter than +P. Both are safe to use in 9mm Glocks.
3) Yes. The Glock 17 was created for the Austrian army and is now in use in many other armies. It was designed to use military and SAAMI (commercial) ammo.
4) Glock warns against using handloads in their products. In fact, I'd be willing to bet that most of the KaBooms that you hear about in Glocks are caused by the use of handloads (improperly loaded or otherwise.)
Now, to my knowledge, the whole non-supported chamber issue in Glocks does not apply to 9mm models. I've read that Glock only did it in their other chamberings (.40 S&W, .45 ACP, 10mm, etc.) to achieve reliable operation. But just to stay on the safe side, I wouldn't use any reloads (even 9mm) in Glock pistols.
5) I buy my 9MM from Academy Sports & Outdoors for $4.86 per 50. If you do not have one around you (I think they are only in the south), then Wal-Mart has pretty good deals on Winchester White Box (WWB) 9mm.
Glocks are good pistols. Shoot the hell out of it, and then shoot it some more.
If you have not already, I suggest you check out
this thread. It really shows you how much a Glock will take and keep on ticking.