I replaced my rocker cover gasket myself a couple of months back. I'm also a complete novice but it worked out well for me.
Remove the rocker cover, peel of the old gasket (I'm guessing it's cork?) and scrape off any old silicone thats stuck to the rocker cover and the head so tha both surfaces are nice and smooth.
Fit the new gasket (the rubber ones are definately the ones to go for) and use some gasket silicone like Xploded EA said.
3.9 CFI Falcon. King Springs, Monroe GT Shockers. Formula 1 Tinted windows. Pioneer 3350 Head Unit, 12" JL Audio Sub. 6"-9" Pioneer 3 Ways, 4" Clarion 2 Ways, 500watt Schneider Amp, 222watt Sony Xplode Amp. Really shitty 14" Jelly Beans