Long ago I built their L-1011, but never go to do a 747. The L-1011's assembly was much like any other kit except for the landing gear being made up of many parts (wheels, hubs, brakes, strut pieces) -- I don't recall the gear being particularly hard, but if there were 18 wheels I could see where it might get tedious -- just do a few at a time as you are building the rest of the kit. None of the flight controls on the L-1011 moved and the flaps were molded up as in a typical kit. There were also some extra parts in the kit which were not mentioned by the directions, and I figured out these were pitot tubes, a tail skid, and I don't recall what else. Can't recall any interior parts on the L-1011 besides bulkheads and landing gear wells.
The L-1011 is an excellent kit, so their 747 probably is, too.