The rear main seal is directly in front of the flywheel/driveplate. You have to remove the rear main bearing cap and pry the old seal half out of the bearing cap with a small screw driver. To remove the upper half, simply use a small brass punch and hammer. Carefully tap the punch upwards on one side of the seal, it will turn and start coming out the otherside, once you are able to get a pair of needle nose pliers on the protruding side, pull it slowly out until the full half is removed. Avoid damaging the crankshaft with the hammer. Remember there are two pieces to this seal, upper and lower halves. If you're still confused go out and buy a Haynes Repair Manual for your rig, Good Luck,
James