reza

Yes, you need to remove the engine [and transmission as a unit per Nisan] The front crossmember does not allow for vertical drop of the oil pan.  Removal is easier if you first remove the cast valve cover due to wiper motor interferrance.

Thank you! and bummer! 

Further caution if you have the automatic transmission.  There is a socket molded into the lor driver's side of the engine block and a corresponding socket attached to the left front rail.  They are for the complicated automatic transmission shift lever mechanism. and have rubber boots.  Be careful and don't loose the boots.