I would say that rebuilding one of these motors requires a bit of mechanical knowledge, some special tools, and a lack of fear of tearing into one of these. Me personally, I'm better at the external parts of the bike. Getting into the internals of one of these motors scares me a bit.
One of these years, I'll get a used engine and see about rebuilding it.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.