Having made that trip to Fairbanks, Alaska many times, I'd think you wouldn't need the A/C for the entire trip up and back to Montana.
Like R2Home, I'd wait. But in my case, I'd wait until I got to Mexico and have it done there.
But, there is a highly thought of RV dealer in Whitehorse, Yukon Territory, Philmar RV. Then, across the street and a mile away from Philmar, I've had work done at Fireweed RV services on my refer that was fast and, well, not exactly cheap, but about what I expected for service in Canada. Plenty of RV parks there too.