Yuck! Can you smoke them out? Maybe light a small charcoal grill in the garage with something that'll cause a lot of smoke? Maybe the smoke will get into the cracks and make the bees leave?

Otherwise, I'd be on the phone with an exterminator first thing tomorrow morning! Now I'm all itchy from thnking about gobs of bees crawling around! I'm highly afraid of bees! More so than spiders!