Okay, so after doing some googling about installing the ARB reversing camera and not really finding anything (I guess most people get it installed by the workshop), I nutted it out myself and thought I'd put it up here to help others out. It's not hard by any means, but there's a few little things that might leave you thinking for a while.
First things first, it removing your old rearview mirror, as the ARB system comes with a replacement which has a small LCD screen built in which lights up when in reverse. The OEM mirror has a small plastic shroud over the metal "button" which the mirror arm mounts to.
This is removed by gently twisting side to side and pulling, it has two small plastic clips which hold it on. Once this is off, you just need to get a flat bladed screw driver, (preferably wrapped in electrical tape so you don't scratch your glass). To remove the mirror arm from the metal "button" on the windscreen,all you need to do is, using the screwdriver, press the plastic tab on the underside of the mounting point down towards you, and pull the mirror assembly upwards. You may have to rock it back and forth a little but it should just slide off (this is on an 08 model, not sure if later/earlier ones are the same). Here's a pic of the mounting assemble once off showing the plastic tab, and how it mounts to the metal button.
And the metal button left after removal
Next step is to slide the ARB mirror onto the mounting button on the windscreen and tighten the grub screw to hold it on. The ARB mount is slightly different to the OEM one, and needs the grub screw to keep it attached, instead of a plastic clip.
Next, route the video cable for the mirror up under the lip of the roof lining. If you have some small convuluted tubing it would probably help prevent the cable from coming out of the lining, but I didn't so just pushed it in. I did however remove the passenger's side sunvisor so I could push the cable in as far as I though necessary. The visor is held in with 2 screws on the door side and a screw with a plastic plug (pictured below) on the inside. Just remove the screw and gently pull the plug out. Push your cable in, and push the plug back in after, tighten screws.
As I chose to run the cable down the passenger's side, I then removed the A-pillar panel and ran the video feed cable down inside it. It is held on with two #2 Phillips screws and 2 plastic plugs which should pop out if you gently pull the panel off starting at the top.
This will expose the existing wiring (I assume its the courtesy light wires) and a few clips to hold the new cable in place as well. I also used a few small zip ties down at the bottom of the cable run before it drops under the dash.
I didn't get any photos of it at the time, but I dropped the video cable under the dash and secured it near the small fuse box on the door side of the passenger's footwell. I also bundled up the excess wires from the wiring harness and secured them all there with a big zip tie to keep it neat (I will be tidying it up later).
I ran the red power wire through the firewall using the existing "nipples" on the main grommet on the pass side, connected the black earth wire to an existing earth point in the cab and ran the orange reverse signal wire to the driver's side fuse box, to the lower left of the steering wheel. After a quick call to ARB Darwin for some advice, I attached the orange wire to the red wire with white trace.(
viewtopic.php?t=12142#p178551) Apparently you can aso use a wire on the passenger's side fuse box (
viewtopic.php?t=12460#p263025) but I wasn't aware of it til after.