Jack,
The display has a lip on the top it simply pops off and then in some cases you can either remove and reinstall the snap on power connectors or you have to cut and splice it back in. The RJ-11s just snap in, but make sure you plug the right ones back into the right places or your grey will register your black, etc and will be way off.
Not a hard job by any means, but getting the unit back in can take some time as you have lots of wires (RJ-11 and others) to get back into a not so deep space between the inner wall and outer wall.
To get to the LEDs you'd have to remove the circuit board from the plastic face plate, unsolder the LED and re-solder a new one....far easier to swap units IMHO.
I too don't run the unit while in transit, though I have checked levels at a rest area, the batter power was not at even full power FWIW. I have a good email address for you to use Jack....check your PMs....