We did this trip 3 years ago and will most likely do it again. The only change is that we will most likely do it solo. Traveling in groups can lead to un-planned problems. We did the trip in a 33 ft fifth wheel we had at the time. A 45 foot MH is on the large side but not a deal breaker. A little advance planning will be needed as most rigs that size make it a little tight in some places but no impossible.
As far as guns are concerned, leave them home. You don't need them and will get into trouble entering Canada. If you feel you really need a firearm in Alaska, just buy one when you get there and then have it shipped home before you come back through Canada. Most all of the wild animals you will encounter want nothing to do with you.
There is plenty of liquor available in Canada. If you try and bring too much through they will charge you import duty.
Keith