I'm sure the "oil" you refer to is in fact the "brown menace", cosmoline. These SKSs have a reputation of being engorged with the crap.
DO NOT fire the gun without first cleaning the stuff out. You could easily cause a KB with a barrel that is probably completely full of cosmoline. In addition it's probably seized your firing pin in the bolt as well. My friend cleaned his out with a parts cleaning tank and it still didn't get it out of the bolt, and the gun wouldn't fire. It would barely nick the primers.
It's not that hard to clean out, but it does take some time and a LOT of rags or paper towels.
I took mine apart and put all the small parts in an old pot and boiled them in water on the stove. I took the bolt completely apart, the bolt carrier, springs, top cover, magazine and tigger parts, gas valve, every thing that could fit in the pot went in. The cosmoline, like oil, is less dense than the water and when "boiled out" will float to the top. The boiling water drys almost instantly and only an occasional scrubbing was needed to get the thick stuff out.
When I took the parts out, I wiped them down with a rag soaked in Breakfree and set them aside.
I used gun scrubber and LOTS of paper towels, rags, Q-tips, toothbrushes, and toothpicks on the barreled receiver.
The stock got the heat gun treatment. Heat and wipe, heat and wipe. It's not absolutely beautiful and grease free!