[villagetinker]

OP, no idea of how old sealer would be removed without damaging the paint underneath. IMHO, you could try calling some of the several vendors that provide driveway sealing and or painting services, and ask if they have ever done this successfully. Then get references so you can verify their solution actually works.
I would expect most will tell you to have the old finish completely removed (sand blasting or grinding), and then have a new finish applied. NOTE: if you have the driveway finish ground off, the painted finish will be very slippery, make sure you get an antiskid (like shark grip) additive on the final coat. When we had this done the person we used (driveways by Jay) used double the amount of shark grip to make sure we did not have a slippery surface.
Hope this helps.