The vehicles will have 1 metre clearance on the engines and then will have to be manoeuvred into place with some finesse as they avoid the all composite wing trailing edges.
You are talking about different sides of the wing, for the doors in front of the wing, the inner engines are quite close. For the doors aft of the wing probably the flap track fairings are critical (that´s why their tips are
painted red at the moment...). The trailing edges of the flaps (three each side) are aluminum, the skin is composite. So a minor hit would probably just dent the aluminum end profile, a major one would require extensive repair.
For catering the upper deck, an optional trolley lift is available, I´ll bet it will be used quite frequently instead of using special upper deck trucks.
One benefit of the A380 size is that the all composite tail section is well above the ground, so you will need a huge truck to hit it
The whole aft end of the aircraft is composite, and no engineering manual exists (or will exist for approx four years) on how to repair the composite structure should it be damaged by a catering truck
As already said, all the fuselage sections containing doors used during turnaraound are made from Glare. Repair can be done using more or less the same technique as for conventional aluminum. Only the unpressurized tail section is carbon fibre, and not as prone to accidental damage as the area around the doors.
The belly area of the fuselage is aluminum with welded stringers, which is also repaired using conventional technique.