Concur. Clean first. I just did this to my 250 about 2 months back. I recomend using a shop crane to raise the engine. The book says to remove motor mount pass though bolts, loosen (not remove) the tranny crossmember bolts, then raise the engine. Now reinstall the pass thru bolts above the frame portion of the motor mount and set the engine down on it. It's still a tight squeeze, but doable.
BTW, I did it using a floor jack. Din't forget to put a block of wood under the oil pan if you use a floor jack. And it's a good time to paint that nasty ol' pan too......
