I enjoyed building the Weasel during Monogram's first re-release of their armor kits in 1966, and it went together in less than an hour, including painting (consider that I was nine, so that was pretty perfunctory). If you want the whole thing to meet modern standards, you're going to have to scratchbuild almost all the surface detail. The hull detail is crisp, but it is all molded in place, so for every part, you'll have to decide, sand it down and scratchbuild a replacement or just dry brush and move on. Suspension, likewise, is just a couple of parts, and nothing to suggest that there were four wheels per axle. Again, modify, replace, or just let it go--it's up to you. The sideskirts disguise much of the missing spring detail, but that would have to be added if you wanted to convert it to the basic, non-amphibious M29 Doodlebug. The rudders and the support arms are massively thick, so thin them down or replace them. Photoetch or real wire screening for the muffler cover would be a nice, eye-catching improvement. The real tracks had a wire reinforcement outboard of the wheels, which could be added from fine wire and superglue. I've thought about building one I've stashed since the re-release in the 1970's, but it would be a six week project to do it absolutely right. I guess if I ever build it, I'll just replace those details that are most likely to be noticed and let the rest slide (Shep Paine's diorama for Monogram's 1973 edition featured the Weasel surging up out of a marsh onto a muddy bank, so the kit's worst sins were covered by Plastic of Paris swamp water--very slick).
