Few questions after an easy start :)

Hi mates!
Well I just installed Xandros on my Dell 8100 and everything went juuuust fine . I'm having a problems with resolution but I guess installing nvidia drivers will solve this.

But being new I still have a few questions

1. I'm mainly gamer/tweaker when it comes to computers, but I'll use my main rig for those purposes. Thing is I don't understand anything when it comes to Linux, how file system works, how the programs are saved (Program Files map), where are the system files and stuff like this. I guess I'll have to unlearn Windows first before I plunge into learning Linux. Anyway what is the good way of doing this? Any documentation on this topic that I can find online?
I'm just so overwhelmed, don't know where to begin
Any other things you vets (or learners like me) would recommend me to start with/learn/read about? Just bring it on!

2. I'm planning to start programming again Haven't done it for like 3 years now. Knew a bit of C++ back in the days but have forgoten most of it by now I guess. So what program should I use? Good development tool?
If it ain't in Xandros by default I could install it (would be good practice that too )

3. About updating KDE or Gnome... I guess Xandros uses KDE as X... if I was to install latest KDE... Would that fubar Xandros system tools, delete all the shortcuts on desktop and all of those nasty stuff ?
I would like to play with all kind of window mangers (if that is the way you call them) and see what I can learn from that

That would be it for now
Any info would be greatly appreciated!
Thank you for your time!