Well, I've never built an aircraft, but in maintenance, the galley units are amongst the first things to be taken out and nearly the last major item to be put back in!
I can't speak for all aircraft types, but from my experience the galley units are split inside the aircraft before removal and re-assemble inside the aircraft when they are put back in. I guess this is fairly obvious though as some of the units are quite large! This can be quite a pain because they are often large and awkward items to move around. There's no way you can get lifting equipment in to the cabin, so you get as many blokes as you can to help move it around and position it!
For example, on a 737-800 the aft galley and toilets can be installed first along with the fwd toilet and fwd L/H galley unit. The seats can then be loaded and installed followed finally by the fwd R/H equipment stowage cabinets.