Engine/drivetrain vibration?

You could do as you are talking about with taking the transmission to the shop, but if the balancer did slip and that is causing your vibration as redfastback gas suggested just balancing the transmission to the balancer will not prevent the balancer from slipping again.

If you don't want any more problems with your motor replace the balancer and instead of putting weights on the torque converter install the B&M Flexplate in the link below. The bolts only line up one way so the weight will always be installed on the correct side of the torque converter.

If the vibration is still in the car have your driveshaft balanced.

http://store.summitracing.com/partdetail.asp?part=BMM-10235&autoview=sku

Hope this helps.