Hi how are you .
as far as not getting into drive, it could be several reasons, the linkage broke ,shifter, did you inspect fluid ,seized etc.. it needs to be inspected
do you still have a warranty since only been 2000 miles ago on transmission?
was the transmission shifter loose or getting stuck prior to this happening ?
1- I will absolutely keep the 1969 280 SL since the value of this car keeps on going up and it is considered a classic car and very desirable
2- the 1998 SL500 might be your call on this one ,if you considering, paying insurance taxes ,and do you needed since you have the genesis etc.. depends on mileage of car how many miles ? but if it is one owner and your husband took care of it, then i dont see an issue for repairs if low miles if high mileage then this one i will consider selling
3-the genesis is more practical on daily base , the other are Sunday cars , but the 1969 SL is a keeper.
4- it is not that expensive to keep up the 1969 , I would store it in a garaged area if possible or at least covered and always service the fluids to keep in good condition and only used oem fluids and parts and keep all the records
Please let me know if that works for you
ASE Certified Technician