People looking for FreeWindows XP tend to be disappointed; UNIX is not Windows. Be warned. You
will need to do things differently. There are myriad differences that not even Ubuntu can hide -- and I'm not exactly for hiding these differences anyway, why obliterate indispensable features just to ape an OS everyone hates?
Re: #1, you can download a
Knoppix livecd to boot on your computer. This can run a full Linux desktop without installing anything on your computer, good for trying things out. For a full installation, I won't even get into that argument since most seem to hate my distro of choice.
Re: #2, the desktop is
not the kernel. It's just a program. In Windows they are inseperable, but UNIX is not Windows. You may have seen Sun's experimental 3D window manager, which might be a cool toy, but probably needs a high-powered video card, and likely isn't too stable besides. Get your system working first is my advice, then worry about cool toys.
Re: #3, difficult to say without knowing what window manager he was using; There's no "standard" Linux desktop environment. There's some popular ones, but if he's using that 3D window manager there's no telling what other bizzare things he's got running.
If you're limited in time and need to run windows programs for school and games, skip it and come back to it when you've got time to learn how to use your computer from scratch. Otherwise you'll just end up an irrational linux hater like I did. I eventually converted for the same reason as you, cost, and have discovered many reasons to stay, but spent weeks in "wonder what this button does" mode.