Yes, and Yes. You will need to register your guns with US Customs prior to leaving, so that when you enter Alaska, you can prove that the guns are yours, and you are simply bringing them back into the US from Canada. That registration is good forever.
Yes, you will need to register your guns going into Canada. If I remember correctly, there is a fee of about $25, but I don't remember if that is per gun or a one-time fee that can be applied to a number of guns. I believe that form is good for 90 days. Google up "Canadian Gun Laws", and you will be directed to a Canadian site which can answer your questions
In each case, if your border port is like Detroit/Windsor, DO NOT bring the guns into the office. Have the serial numbers, and if the agent wants to verify the numbers, he/she will come out to your car.
Good luck
