There is an oil seal behind the parking brake assembly that is probably brittle and cracking. Yes, there is a gasket back there as well. Did you check that there is oil in the transmission? Be careful, because there is likely a leak between the transmission and transfer case, that can cause the fill plug on either transmission or transfer to overflow, so be prepared. You will need a new stake-nut as well as a seal and a gasket; if you can catch your fingernail on the sealing groove on the brake drum you will need a speedi-sleeve to smooth the surface. Easy job, but make sure that the brake shoes are properly adjusted when you are done; if necessary adjust the parking brake at the cable on the firewall.
Mine is leaking there as well.
