Hi Brian, for centering a group of several objects, select them all, then run the Transform/Move command.

Pick the first point at your best guess of where the center of your group is at. If you have a hard time judging the proportions, you may want to draw a rectangle to frame your group first, then you can snap on to the center of that rectangle.

Then on the second point of the Move command, pick on the origin.

That should do it.

If you're having difficulty with a particular group of objects, can you please post the model file here? That will help me give you more specific step-by-step instructions.

- Michael