You see Avanina, the terminal isn't bad at all, you should always learn the basic commands.
eg. Removing all files with a specific extension, or even folders. One command :P Moving them, copying, making folders. It's all so much faster.
Also when you run into problems you can ALWAYS go to a different TTY, log in and work with the console. :) (Alt + any of the F keys. I believe F7 returns you to the graphical user interface, give it a try).
Fear is your enemy in Linux.
Pro-tip: Try basic commands in a new account (not the one you use, nor the root -- which means no sudo). If you mess up, it's only that user :)
Yes, you can. But take backups to be safe. Make a partition for Linux, depending on which distro you pick, most installers will offer you a chance to set up a bootloader and flag which OS you want as default etc.
Just so you know, should this "break" your windows boot up, which has happened to me (hard drive - motherboard issues), you can pop the xp install cd in, drop into the repair console thing, type fixmbr I think it was (should you need it, I can find the note). (This is of course when you drop the bootloader info on the mbr)