Sounds like mud daubers,or other pesty insects found a place to get into the engine and make a mess of things. I had a mouse nest between the clutch-disc/pressure-plate,that made a mess of things,as well. Urine "froze" the parts together. Doesn't take long for critters to play havoc with "our" treasures. May need to pull the pan,to inspect your "bottom-end",but it sounds like a complete rebuild,or engine/tranny swap.
