1988 Pontiac Firebird clutch release issue

I have an 88 firebird, the clutch was replaced about 8k miles ago. The car over time since then has seemed to have the clutch not fully release, and has gotten worse. I inspected all components, and they seemed fine a while back. I noticed however, that there is oil in the bell housing, and the clutch seems to hang up more when the engine and drive train has warmed up. I dont experience any slipping, but is it most likely the clutch has become contaminated and is expanding? The only other thing I can think of besides a pressure plate or clutch is maybe a pilot bearing that wasnt replaced with the clutch set. Any input is greatly appreciated.