The oil pan can easily be replaced with the engine in the car and the engine does not need to be raised up. It will be necessary to remove the right tie rod on the outter end and to unbolt (4 bolts) the little rear cross member.

You can replace (easily) the lower half of the rear main seal at this time. Some attempt to pull thru an upper seal but can be a real core and after its strectched out it will still leak. I would suggest packing the ends of the old top seal with a blunt object and cutting pieces off from the old lower seal to fill the gap. This was an approved way of fixing the seal leak on the last Oldsmobile 8 cyl engines.

When replacing the oil pan gasket the side gaskets must be stuck up onto the block first and then the end corks inserted into the main bearing caps. Pre-curl the end corks before installing. Sabes a lot of swearing. I uses 4 little studs , insert them into the blaoc, to guide teh pan straight up into place. This helps to prevent the gaskets from slipping.

While the pan is off attach the garden hole to the main oil pipe that feeds the troughs. No uncommon to find a pipe that is plugged up.