Access to the internals are through the side opposite the flywheel. Are you saying that you are having trouble pulling that side cover off?
It's been years since I've cracked my case open, and I rememeber Tecumsehs having a C clip around the driveshaft that has to be removed to pull the case cover; but I don't remember that being the case (pardon the pun) with the Subaru. Try turning the cover and wiggle it back and forth as you pull it off. The governer guts may be hanging on inside of there.
If all else fails, reference that Subaru manual page, and check out the service manual for their procedure on dismantling the engine. This manual will be a must, as there is a specific procedure to putting that cam drive chain back into the engine and getting the cam timing correct.