From the supplied pictures, I'd highly recommend cleaning it up. Heck, I used a pressure washer on mine when I got it ( kinda looked like yours ) with no ill effects.
The gaskets for the cam covers are not known to have any leaking problems, as long as the torque on the bolts is correct. ( 10 Nm / 7 Ft # / 84 inch # )
You need to order a set of male and female Torx sockets, 3/8" drive is sufficient.

Through RockAuto :
http://www.lislecorp.com/divisions/p...s/?product=122
http://www.lislecorp.com/divisions/p...s/?product=126

A note on the vent covers : make absolutely sure you get all the old RTV sealant off before resealing them.

You can easily remove the valve covers for cleaning and resealing by removing the 6 coil pack connectors, then the 6 coil pack bolts and then laying them back out of the way. ( also the vacuum line on the drivers side ).

Might as well order a new pair of rubber gaskets for reinstallation after they are cleaned up and the vent covers are resealed.

( 2003 MERCEDES-BENZ SLK320 Valve Cover Gasket )