Just drove up and back from Washington State last month. Roads are in pretty good shape.
Yes, American credit cards work fine. Some fuel stations want your credit card inside the station before they'll turn on the pump. Late in the day, some stations close early. Use caution, it would be easy to end up waiting for a station to open.
Cassiar highway is beautiful. I took some time for hiking, camping and photography along the way.
Registered my rifle with U.S. Customs before crossing, and glad I did. I think it was a $25 fee to take the gun through Canada, and they really liked that I had it in a locked case.
BC and Yukon Territories have some nice campgrounds along the way at very reasonable prices. I camped most nights, up and back. Just parked my Jeep, put up my little tent and enjoyed. Canadian currency was very useful to pay for the campsites.
The paper map in the Milepost was great! It's all I used during the drive. Not that it's a complicated route.
Enjoy the drive, give yourself plenty of time.
Regards, Guy
