Take someone from the shop for a ride on the highway, when it shakes ask them, "Can you feel that motherfvcker?" If they lie and say no, backhand them with a tire iron or wrench, open the passenger side door and push their ass out at 70 mph. Shakes like you describe are common on superbeetles. My struts were worn on the bug, when I replaced them, along with most of the front suspension, the shakes were gone. It may also be that the shop took it for a test drive and clipped something, that would knock your alignment off and possiboe cause symtoms like you describe.