The handle comes off by loosing a torx screw which is under a rubber plug, you should then pull the handle and it locks "open" and the entire thing comes away. Couple of connectors to unplug at the front end.
Then you remove the "guts", from memory the keyless bit comes out first then the LED module.
Reassembly is reverse of the above. That said, more than once I had a nightmare with a handle, clearly had been off before and was broken. Dropped part of the mech inside the door, had to strip the full door to fish it back out! Good luck
I'm not sure how much the dealer is charging for the part, but I have replaced two sets on D4s, with LED's from Aliexpress which cost <£30 shipped for the full set from memory! When one goes, they all usually follow.