On a 300E, the procedure isn't too bad, assuming the plugs haven't been left in for a hundred thousand miles. I don't have pics, but I can give you a rough procedure.
spark plugs (x 6, use the bosch copper ones)
dielectric silicone grease
spark plug socket (or fish around for a metric size that's close enough)
can of compressed air
1. Pull off spark plug wires (pull from the wire boot, NOT the wires. If the plugs haven't been changed in a LONG time, they will be very hard to unseat. Generally, a pulling/twisting/rocking motion will eventually get the wires off. There is a special set of pliers you can buy that help, but they shouldn't really be necessary.)
2. Blow out spark plug wells with compressed air.
3. Unscrew spark plugs. Take a second to check the condition of the plug electrode (the metal bit sticking out from the center of the plug) and the insulator around the electrode, they can tell you a lot about that cylinder.
4. Coat the new plugs with a little anti-seize (on the screw threads) and dielectric grease (on the ribbed porcelin insulator that the plug wires attach to).
5. Screw the plugs into the engine. Be careful not to cross-thread the plugs. (I usually start them by hand with the socket and the extension, then use the ratchet when I can't hand-tighten any further).
6. Torque all of them evenly to about 15 Nm or so (may want to check this, memory's a little fuzzy).
7. Re-attach plug wires.
8. Start engine and check for any misfires, etc.
2000 C 2 3 0 Sport :: 180k