I have modded the game when I had the disc but I got a new (not ne wbut new to me) Laptop and want to mod the steam version. I need to find a step by step instruction of how to mod this game. Please help.

Its the same as the disk version, other than the location of the installed game (which can not be in Program Files or Program Files(x86) )

If your using script extenders then you need to enable the Steam Community (it's that or the 4GB patch but the readme's will tell you what to do with those) But other than that, modding the game is the same as it was before.

Did I mention don't install this game in any of the Program Files directories?