Re-Paint ??... Pro's Chime In....

Use a good epoxy as a sealer and you won't have any issues. As long as you sand the existing finish properly it won't be a problem. Sanding and refinishing over old substrates happens all the time. Not every paint job is striped to bare metal. Sand it, clean it, surface prime where needed, use epoxy as a sealer, base and clear it and done.