changing sparkplugs on w209 clk320

[Tango]

hi could anyone tell me whats the best way to remove and change the sparkplugs on this model, its the early 2002 newer shape clk320. i wanted to take a hand at doing this myself on this car. but when i remove the leads from the spark plugs there seems to be a sharp triangle object covering half of the hole so as i cannot get the socket wrench in there.. any merc specialists on here to give any ideas?

thanks!