Very little is prefabed.
Ty: was your fuselage prefabbed? The ones we got from Tom had prefabbed fuselages and were well-shaped. The wings were his typical "Millenium" design, and he had already put the leading and trailing edge pieces together. Granted that wing has many more parts because it is sort-of like an I-beam wing using rib-strips, but it wasn't too hard to assemble using his wing-blocks.
We did ours as a club build and had Saturday building sessions to work on them. Some of the guys who couldn't make the sessions had a hard time with the wing, but I think that most of ours got built. We are a typical club with a variety of building and flying talents, so the building sessions were a help to those who weren't regular builders.