EJ20 forum has at least a couple threads on this. Passenger valve cover gasket is the first to go due to it's proximity to the uppipe and turbo. Lots of "shade-tree mechanic" type people have done it themselves. The only issue is that the little bolts will snap if you torque them. The torque rating is 3.6 ft / lbs (next to nothing).
You need the main gasket, the 2 spark plug gaskets, and I think it's 8 little gaskets for the little screws, plus some threebond / fujibond / permatex for the cam seal half-moons. Check the EJ20 forum for part numbers, or get the kit from Rock Auto (kit doesn't include the RTV gasket maker stuff).