I took out the crank position sensor (ref). The one by oil pan under crank pulley. It was covered in oil. Is it supposed to be that dirty and oily? I cleaned it and reinstalled but wasn't sure if that normal for it to be covered in oil.

 

No, it's not normal for oil to be outside of your engine.

Are you going to post a new thread for each one of your questions? Try to keep it all in one, hmm?

http://forums.maxima.org/showthread.php?t=550292

 

Prolly your upper oil pan gasket or crank seal...as pmohr said keep it ALL in one thread.