Matt,
Congratulations. You are now officially addicted to nitro helicopters. Welcome to the dark side.

Re vibrations, check the main shaft and feathering shafts. If the previous owner crashed and didn't replace them, they will likely be bent. They're usually pretty cheap to replace. Remove them and roll them on a flat surface, or just rotate them and observe them. Those are the primary causes of vibrations, given blades are already balanced and tracking is correct.

Mack