Sending the ECM away

[Hammerhead]

I can't help you with the Mack part of the equation, but I am in the Edmonton area...

I wouldn't use mail, Canada Post or USPS for return. Pay the extra and send it FedEx so you can track it if needed. Both CP & USPS have trackable shipping, but their systems don't play nice with each other for tracking international shipments!
I can never ever recommend UPS in Canada. In Canada it's pronounced "Oops" for a reason, and they bill the $h!t out of ya for doing the customs work! And if they see a higher value on the insurance, they will clear it through customs at that higher value and you will pay through your backside...and good luck getting them to straighten it out when they F-up, and they will! I said when, not "if".
Send it FedEx and do the paperwork yourself and save some serious $$. Ask them for help because you want to insure it for value, but you don't want to pay customs fees or duty on value because it's going out for service and will be returning to Canada. Hint: it's going for recalibration!

I have been to Gearhead's shop, and you are sending it to a reputable place.