I had occasion to try this the other day in a vain attempt to upgrade to LED lamps (see separate thread)
I took a few pics, with the correct tools this is a very simple job. Safety first, because you are handling wiring make sure your ignition is off and key removed, disconnect battery to be doubly sure.
You need a 5p coin (or a wide bladed screwdriver)
Small 1/4 or 3/8 ratchet
10mm deep socket
short extension for socket (you WILL need this!)
You need to remove 1 trim panel and 1 plastic plug per cluster to access the 4 nuts you need to remove. Panel is held by two captive plastic fixings (unscrew 1/4 turn with coin) and same with round plastic plug.
Trim screw location.jpg
You should then easily see 3 of the 4 studs holding the lamp cluster, the one furthest out towards the wheel is buried a little deeper (not visible in this pic) where you will need to use extension on your ratchet. The one circled green is the fiddly one
Slacken off nuts and use fingers for the last few turns .. dont drop em you wont find em again. Be careful of the nut recessed in the round hole covered by the plug, I unscrewed a few turns with ratchet and then used socket on its own to ease this off, keeping it tilted up so the nut stayed in the socket.
careful with this nut.jpg
Once you have removed all four nuts the cluster will be free of the bodywork, and just retained by the loom, you can leave this attached. Just pull the sealing rubber to one side to access lamp holders, these require a 1/4 turn twist to free them from the cluster. Picture shows stop/tail lamp holder with LED lamp installed
lamp cluster free.jpg
As they say in all good manuals assembly is the reverse of removal procedure
Hope this helps somebody and saves trip to the dealer; should take about 10 / 15 mins for this job.