[villagetinker]

From what I have been able to gather from my neighbor and the guy that did our driveway painting, you will need to have the old finished ground off, I have not heard of anyone getting away with sand blasting, chemical removal, and any other process. In general everyone advises against painting over a drive way that has already been painted.
IMHO, if you have a person or company that you want to use for refinishing your driveway, I would have them contract the removal of the existing paint. In this way, you should have some warranty on the new paint job. If you do this yourself, or contract the removal and there are problems in the future, you may find you have no warranty on the new paint.
I would check with any of the firms dealing with driveway finishing as they will probably have the necessary grinding equipment. NOTE: this is dusty, and noisy. Good luck with your project.