Hi, Bob. I think you're right to be concerned about the mechanic's inexperience with electric-assist bikes, but I don't think you should worry much about the quality of the drive system. [One of my ebikes is a Valencia+ and I'm familiar enough with the BionX motors and controllers to be confident.]

If you can ID the charger for us (markings, photos), I'm sure one of us will know how to use it and how it's supposed to behave -- LED colors and sequences, charging time, etc. In any case, Trek won't leave you stuck with defective parts, although they move more slowly than you would prefer. They're huge and bureaucratic now.

The rear wheel spokes on these bikes take a lot of torque, not just on the drive side, and spoke breakage was a frequent early problem. The current spoke spec is better, but they're still machine-built wheels. I'd suggest that a good wheelbuilder true and tension the rear before you ride it very much. Hopefully the LBS where you're buying it has someone who qualifies.

Also, the installation of the rear wheel and the axle nut torque are critical. The details should be in a little "RIDE+" pamphlet that comes in the box with the bike. If you read that, you should be able to check the mechanic, or guide him, as necessary.

I'm sorry this is a frustrating process so far, but I'm pretty sure you're going to love this bike. I'm a big, old guy with some heart rhythm issues and a defibrillator in my chest, so I started using electric assist on my commuter and cargo bikes, to help me stay in the saddle. The Trek/BionX combo is really extremely well thought out and implemented. You'll feel like you're simply riding a bike that happens to be amazingly easy to pedal -- anywhere. And when you don't need the assist, the extra weight won't be much of a burden at all.

Keep us posted.