No need to be scared, at least, not really. It's not thát easy to break your device. But as mentioned before, it does take a bit of knowledge and there for reading up first is a prerogative.

Start with the beginners wiki that HellFlyer linked. After that, make alteration slowly, that is, one by one, so you'll know where something went wrong if something goes wrong.

On the terminal, I have two places for you to get started:

http://wiki.maemo.org/Terminal#Using_the_terminal

http://talk.maemo.org/showthread.php?t=63052

Even though it might look intimidating at first, I strongly encourage you to get acquainted with it, as it will help you detect problems.

If you run into problems, come to the board here. Do not forget to past your error messages if you are looking for help, as they greatly improve chances of geting things solved.

Enjoy playing!