That is another question, repairing the carbon fiber vs. aluminum skin. Since it is baked and essentially one big solid piece lets say some moron runs the forks of a forklift through the body of the plane, what is the repair cost and structural integrity afterwords compared to just replacing and re-riveting the aluminum skin of aircraft now?
I find it interesting that the 787 can defer repair to the damage from a lightning strike, but an aluminum skinned aircraft has to be repaired right away.
Also remember that Boeing has experience with the composite tail on the 777.
Not a problem. Although carbon is a bit harder to work with than fiberglass, it isn't hard to repair at all. As a material, it's harder to work with, mostly because it's hard on tools such as drills and cutting implements. It also conducts, so static can be an issue.
One problem with carbon is when it is bent to the point of failure, it very often fails almost explosively. If, for incidence, you take a carbon tube, such as a windsurfer mast, and bend it to the point of breaking, it doesn't just snap like a twig. It explodes and delaminates. The result is very often not repairable. OTOH, if you punch a hole in a carbon sheet, such as a wing section or fuselage side, it's easy to repair.