Joy A. here.........I always carry extra stuff for the trailer, rivets, wheel bearing, fuses etc.. What I did do for Alaska was add some of that clear plastic stuff to protect the front of the Scamp even though I had mud flaps across the back of the Jeep. I placed it from the bottom up to the belly band and from the door around to the refrigerator
door. The underneath of the trailer was fine, needs nothing done to it.
As for tires
, simply carrying the normal spare for the tug and trailer is fine. However, I would recommend that you make sure the trailer tires are new or next to new as 13 trailer tires can be hard to come by.
I didn't carry extra gas however I think in this economy I might do so if I were traveling to Alaska. Maybe just one 5 gallon can. I'd imagine some of those little gas stations I stopped at may be close now. I found gas pretty much very 100 miles in 2006 and also never let my tank go below 1/2. Better to be cautious.
Now for the tug...I aways have jumper cables, an air pump, fuses etc. I did add to my stash a fan belt and air filter. I thought they might be something that could be hard to come by. If I had a problem with either a simple backyard mechanic or handyman could install them for me. Push came to shove I could it. I carry a tool box.
I made a gravel guard for the Jeep out of hardware cloth and PVC which I tied on the front with zip ties. It was a little overkill but did come in handy one time when an oncoming Semi toss a large rock right up into what would have been the grill. My windshield faired OK with exception of a large ding, again from an oncoming Semi. I still have that windshield and "badge of honor" ding, from the Alaska trip on the Jeep. People always ask when I'm going to have the windshield replaced, obviously not very soon. The ding is just a large blob that isn't in my line of sight, with no crack traveling, as often they do.
People have heard lots about the Alaska Highway but it's a piece of cake. 90% of it and all the other roads you'll travel are fine paved highways. I worst part of the highway is from Whitehorse to the Alaska border. I don't recall anything else but there could have been a few frost heaves in. I don't think so though. My recollection is that the nasty part started on the north side of Kluane Lake to near Beaver Creek.
I can't speak for the Top of the World Highway as I opted not to pull my trailer over it and was glad I'd made that decision. Lots of people I spoke with implied it wasn't worth the effort. The road out from Chicken to Tok evidently isn't not all that great. Several said they had to dodge trees right in the middle of the dirt/gravel road.
My dog, Lily, had an intestinal problem by the time we got to Fairbanks so I didn't do the Dalton highway. Had I considered doing it I would not have taken the Scamp. I was considering a simple drive up as far as the "Circle" but again didn't do it.
I willy nillied it and did just fine finding campsites however, I recommend that you make sure you have reservations for campinng if you are near Anchorage or Seward on the 4th of July. Also it's a good idea to have reservations for Denali. I found most campgrounds were not even 1/2 full and I imagine the economy now might have some of them closed but surely not full.
Just be sure to take it slow and have lots of time. I took 2 1/2 months to do my trip. I figured I'd never get back there. I do think about another trip maybe some day as I surely enjoyed it.
PM me if you have any questions.