the sealed bearings on the rear wheel of my six pack are binding up really bad. The side with the freewheel is a sealed bearing and the opposite side is just loose ball bearings. Can I just tap out the sealed bearing and replace it, or am I SOL and have to get a new hub?

You can just get a new bearing.

Like WTP said you can most likely get a new bearing. E-mail DK or go to your local shop and see if you can buy one and have them press it into the hub.