As a woodworker and audio junkie I have looked at doing it and the one advice I can give you is do not sand the veneer. As mentioned above it is too thin. Use a scraper available at Woodcraft, Lee Valley, Rockler and the sort all with web sites. Scrape in the direction of the grain and that will remove the varnish layer and leave the stain.
You may want to re stain to unify the color, then just apply the sealer and topcoat of your choice.
You may want to re stain to unify the color, then just apply the sealer and topcoat of your choice.