Passenger Side Windshield Wiper loose, how to tighten?

Hey,
I have a 93 Civic EX Coupe. For awhile now, my passenger side windshield wiper has been loose. The base where the arm ataches to the motor moves around quite a bit, and when i drive over 60 mph, the blade lifts off the windshield completely. I was told by my mechanic that the only way to access the motors is to rip apart the dash, tighten and put back together. And with all the labor, it would cost about $500. I wanna save me some money, so have any of you had a similar problem, and how did you fix it?

Thanks for any feedback.