Another update - I let the penetrating oil do it's magic overnight and this morning, I cleaned the surface of the lens mount and camera with a rag soaked in isopropyl to get the oil slick off of it. With a clean rag I was able to get enough of a grip around it to slowly but surely spin it off the camera:
The lens, other than some debris and a tiny bit of haze, is remarkably clean. I looked hard for scratches on the front element but couldn't find any - i'm guessing this camera/lens has sadly spent most of it's life in the leather case it came in, likely tucked away in somebody's damp basement.
The aperture tab on lens is locked into place - the next project is to get it CLA'd. I haven't decided whether I want to tackle that myself or take the easy way out and take it to somebody