[Untamed]

Yeah a top-down view first, with scaled measurements. Note windows, doors, bump-outs for any duct / electrical work behind walls, etc. Also note any columns in the center of the garage. Is there any attic space overhead? You might consider recessed ceilings to get more height out of the garage.

Now, having said all that, just remember this is your -mothers- house, Matt. Most people don't creat "dream garages" until they're in their 40's, own their own home, have a career and family of their own. Long way to go until that point. However if you enjoying spending time on the computer drawing up floor plans, more power to you. Personally I would spend the time working on the car.

Good luck!