Home court gives a boost only to both perimeter and inside defense team ratings, and to rebounding. Using the Coach Parrot spreadsheet, you can estimate what the effect of changing home versus away is on team ratings.
In terms of point differential, the conventional wisdom is 5-10 points as strilfe points out. But if your team defense is really crappier, or really better, than your opponent, you might not see as much of an effect on the point outcome.