Replace the plastic fittings on the oil tube. They will be VERY brittle anyway, and will most likely get broken while you are changing the seals. This will oil starve the camshaft and ruin it and the rockers once you start driving it!
Start it up with the valve covers off and verify that you get oil dripping off the tube onto all the rockers after you get the new seals on.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!