Sorry to here about your father passing. My father is in his mid 80's and the thought of him passing is something I think about and fear.

For the door seals, there are two opinions on this. The OEM Mercedes ones are pretty expensive compared to the after market ones (URO is one brand).

However, the Mercedes ones are a far superior product, better material and better fit. Install them once and forget about them for 40 yrs. That is the rout I would take, especially since this car has been in your family since 1976 and has been well taken care of.

If possible please post some pics of the car.