Before you start the game press Ctrl + shift + C if Windows Vista or 7 if XP press rtl + Alt +C. This sjould bring a blue pop up window at the top of the screen. Type TestingCheatsEnabled True and after press enter key the blue pop-up window should disapear if done correctly.
Now with testing cheats enabled while in game press shift while choosing the sim you want to edit. It will give you different choices one of them being edit in CAS press that and Voila!
Note: Make sure to save your game before and after, since there are a lot of posts on the net talking about the game crashing after editing Town, which is what CAS falls under.