I agree with what Gary and Pete had to say about the kits.
They are craftsman kits for sure. You need time, patience, and a few basic tools, but they build up into very nice structures and lineside details.
Over the years, I have built 7 of Campbell's kits. I have one more under construction and three more waiting on the "to do" shelf. Of the ones I have finished, I'd have to say the "Wharf" was the easiest, though very time-consuming. The drawings and templates were excellent. By far, the most complex was "Saez Sash & Door Machine Shop, Shed and Hopper." It was also by far the most time-consuming of the ones I've done.
Of the few I have, if I had to recommend one to someone who had never built a Campbell kit before, I'd say you can't go wrong with "Campbell Supply Co." It wasn't too difficult to assemble, though there are a few "tricky" subassemblies, and it builds up into a very nice looking structure.