If boeing have done their homework [& I don't doubt that they have], the walk-round should not be any worse than for a conventional aircraft. Carbon Fibre Reinforced Epoxies / Plastics - CFRE or CFRP depending on your point of view for how you want to describe them are very tough and resilient materials and will withstand a great deal of punishment, far greater than aluminium will without sustaining any visible damage, or invisible damage for that matter. When they are damaged, it's generally pretty obvious what the damage is. However, like metallic parts damage does not mean that the part is useless as the parts will retain their shape and unless catastrophically damaged, the bulk of their strength.
Having used CFRE materials in the oil industry to protect sensitive electronics inside high pressure/high temperature oil production pipelines I can vouch that they are very robust and are both damage resistant and resistant to chemical attack. As an example, on one of my applications, a 2.5mm thick sleeve was more than capable of withstanding an external pressure in excess of 2200 psi, plus additional imposed bending and other stresses without collapse. The pressure difference on the 787 can't exceed 15psi, so the skin thickness needed to support this pressure difference isn't much.
Conversely, if there is any damage visible on the aircraft skin, then the odds are that something has gone dramatically (catastrophically) wrong on the apron which will be difficult to cover up.
As I said earlier, assuming Boeing have done their work, then any part of the aircraft's load bearing structure which is damage sensitive will be buried well within the skin of the aircraft.
In the fullness of time when more details of the construction of the 787 become known, I think that it will be comparable with the human body in that there will be a load bearing structure with an attached aerodynamic surface structure in the same way that our skin is hung over our skeleton.
And in the same way that we slap an elastoplast over a graze or a small cut, I wouldn't really be surprised if we see duct tape [or gaffer tape if you prefer] as an approved temporary repair method for lightly damaged panels. The odds are that it won't be visible as it will be on the inside held in place by the differential pressure. There is also the option to use self healing CFRP which contains micropockets of resin & hardener that when the part is overstressed, cracked or punctured {on a pretty small scale of course} the pockets are ruptured, mix and cure to seal the breach.
Now as far as the GPU is concerned, the damage to it will probably be fairly evident by the fuselage shaped dent in the cover. That might be a bit of a clue that something untoward has taken place.