Changing 3d text through script

hey, I know how to create 3d Text, and basic GUI, but how do I go about changing what is written in the 3d text? like a score, and when (A) happens you get (+B) onto your score.

P.S. is it possible to stop GUI from moving depending on the resolution of my game?

Sure, just use GUIText.text.

And please don't ask more than one question in a single post (read the FAQ).