Nice to be local.... i'm coming down from Aberdeen! You can always nip home for a decent shower eh?!
I've never worked Arena, only ever campsite or fire towers. It seems to be just patrolling, or stationed at certain places. The main thing we are told are that we are the 'eyes and ears' of the festival and a visual deterrant for general wrong doing but also someone punters can chat too, ask questions, high 5.... stuff like that. I find that being chatty and helpful makes it a more pleasant experience.
Parking is usually quite close to the staff compand - the later you arrive the further you will be but none of it is mental. One of my pet hates about festivals as a punt was dragging your stuff for miles before you find a pitch so from that point of view is so much easier. probably talking 5 mins tops.
Getting there on Weds can mean loads of Hotbox folk turning up and registering at the same time... it can be quite mad. The earlier you get there the better tbh. You could even pitch on the tuesday, register, head home and come back on the weds!
Anyway, enough waffling from me. That answer your questions?