The rear seal is a two piece unit, with the upper half in the block, and the lower half in the rear crank journal. The oil pan will need to come off to replace the seal. It is possible to remove the pan with the engine in the car, but it is NOT easy. The entire front crossmember can be lowered (with engine supported from above), and the pan removed. This is not an easy job (I have done it), and I would not do it this way again. The easiest way (in the long run) is to just remove the engine, and leave the trans and TC in the car. You can then put the engine on a stand, and do the whole job without laying on your back in a pool of oil. Another reason to do it this way, is you can clean and paint the engine before installing it.