The GNS430 is pretty easy to use. As long as you can demonstrate enough knowledge of it to accomplish the flying in your profile, that's about all you need to know. It'll do some cool things but you won't need a PhD in the 430 to pass your check ride. Just know the basics.
Edit: also know how to check for RAIM and ensure the GPS is in approach mode, etc. The Garmin sim should help with that, and its easy to do.