To do this you need some stuff that needs disclaimers and warnings all over the place, as stated before, it's should be very easy to brick your device using and changing any of these apps/repositories/files,...

First you need root access on xterminal
You can get this by installing rootsh from extras/devel IIRC. (help on this topic in other treads on this forum!)

Then you need a program to edit the file
I like to use leafpad as I'm used to notepad on windows.
Leafpad is also in one of the extras repositories.

Now for the real work:
Open Xterm
type:
from now on you have root access (notice the # at the end of the current line instead of the $) so don't do stupid things!

For safety measures copy the mce.ini file.
how I go about this is by making a directory in the same one the file is in and then copy the file to that directory. To do that:

Now open the file with leafpad
and make the changes you'd like to make. Double check your input before choosing save from the statusbar menu! Close Leafpad.

To get the changes you made they have to be reloaded. Force this with this command in xterm as root:

This way you don't have to restart after every change.

Offtopic:
Have to say I learned all this from trailing this forum and great community, makes my N900 experience one of the best yet in phones as well as computer.

Hint:
Googling "linux commands" can teach allot about how to do things the linux way from xterm. move, rename, list content, the use of flags (eg.: -a) and mutch more.
Some general rules: spaces Capitals and symbols matter!!!
One last disclaimer: All in this post I found out by trial and, thankfully very little, error. I don't have a clue about Linux so don't thake this as the right way to do things!!