Piston rings
 

I was wondering if you can just drop the oil pan easily in the car. After head is pulled. Can the Pistons be dropped below easily. Also is there any special tools needed besides the basics?

No, The front cross member is in the way, the sump needs to be lowered enough to clear the oil strainer protruding form the bottom of the block. I've only done it with the engine out, although I have read its possible to dismantle the cross member or lift the engine enough to remove the sump. Personally I would pull the engine, less hassle. (Location UK Sussex)

There’s the culprit.

http://i17.photobucket.com/albums/b5...ilStrainer.jpg