Whether you just want to replace the bulb, or the entire lens
assembly, the procedure is pretty much the same. You have to remove
the paneling from the inside of the back door to get to it.
First remove the two screws from the handle in the lower left corner. Once those are out, there are just plastic clips holding the paneling on. You should be able to pull gently, and remove it enough to reach the bulbs.
If you are replacing the whole assembly, there are four nuts holding it on. One outside the paneling, on the lip of the door, and three under the paneling. You will need a deep 10mm socket to remove them.
I just did this for the first time, and it took a total of about 10 minutes, most of which was spent trying to figure out how to unscrew the nuts without a deep socket.