If the rear main seal is leaking and needs to be changed, it's an engine out job. Don't know about the front. Weird that both seals would start to leak at the same time.
You might try some of the high mileage oil with the seal expanding chemicals in it. The rear main seal in our 89 Milano has leaked for some time, but not really noticeable according to the dip stick, but it does leave a small puddle on the garage floor. I added a qt of the Valvoline(?) High Mileage oil, 20W-50, and it seems to have slowed if not stopped. I also know that it works for steering rack leaks (Lucas Steering Stopleak).
1989 Milano, Shankle Sport
1991 164S, stock
1994 164LS (~Q)
1972 Morgan 27
previously owned since 1964:
62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6