Engine failure after oil change

I suppose I'll need to pull the engine and transmission together, since I can't rotate the crank to uncouple them. Is there any other way?

You didn't specify whether or not it was auto or stick. If it's a manual trans, you could put the car in gear and try 'rocking' or pushing to get the engine to rotate. I'd make sure the spark plugs were also removed to 'unload' any cylinder pressure.

Sorry to hear about the engine and good luck bringing it back to life.

S