Unfortunately for you there is no easy or quick way to fix these walls. Sounds like your garage is built into a hill. You are going to need a good brick mason who has layed many blocks. Check Angies List for your area, and make sure you get references from those they have worked for in the past.
Without digging up the dirt around your garage, the entire roof of your garage will need to be FIRMLY supported with a temporary support system. This could possibly be done one side at a time. Once the ceiling is supported PROPERLY, then your mason can remove the blocks from the inside, and replace them with the proper rebar and/or concrete reinforcement
Whatever you do, get a contractor who has experience in structural support, and check your local building codes. You may need a permit since these are load bareing walls.
Old World Remodeling
Fort Worth, TX