Hey... It is possible to reseal the pan with the motor in chassis, but it is such a pain the beepbeepbeep that it's not worth the effort. You need to clean the bottom of the block pretty well for the new RTV to seal properly, and it is very hard to do with the motor in the vehicle. Also, there is barely enough clearence between the pan and cross member, making it hard to set the pan in place without ruining the bead of silicone that you put on the pan. The 7.3L is very easy to pull as compared to the 6.0L, and you'll probably spend less time on the job if you pull the motor.