[cmiovino]

IMO, unless it's really leaking and causing a running issue, you don't really need to replace the valve cover gaskets. My WRX has been leaking for years with 155k and I haven't replaced them. It's only if you're getting a ton of oil on the spark plug wire/coilpacks that you should. Many times the gasket will leak outside a bit, but it's just not worth the time/effort/cost to do it. I would clean up the exterior if you can - I hate oil on everything.

You should be able to replace them while the engine is in the car if it's like any other Subaru boxer engine. It's just not fun and very tight. I wouldn't pull the engine just to replace the gasket though.