just need to know if i need to take the whole motor out to do this, or can i leave it in.

are you doing a HG job? isnt that the EJ18 motor in that? if its the EJ22, are you putting EJ18 heads on it? aside from my questions, yes you can do it in the car, but i say pull the motor, you will have a much simpler timre while working on motor, and you'll be able to access the rear main seal and oil separator plate.

 

 

~Josh~