Don't know which road you are taking into Dawson Creek, but you might want to go through Grande Prairie. On my trip in 2012, I needed a thermostat replacement on my Ford F350 and decided to replace my problematic fifth-wheel hitch before hitting the Alaska Highway. Grande Prairie had a very good Ford dealership and I had a good experience with an RV dealer there. That will be your last big town before Whitehorse.
Prince George is a major town, but it's a lot further from the start of the Alaska Highway.