Sounds like those are glued - and like others have advised, if the joint is still strong, leave it alone.
Sanding finished wood to re-stain is a tough job. Lots of folks like to use chemical stain removers and although I'm not a big fan of these chemical stain removers (haven't used them in 25 years), I think the new versions of these are probably better then the ones I used long ago.
I'm a big fan of cabinet scrapers which are old time tool used before the invention of sand paper. A good scraper will leave wood surfaces at the equivalent of 220 grit sandpaper but are so much more efficient and aggressive then sandpaper. The only draw back to cabinet scrapers is the sharpening process. There are several conflicting methods and all are correct. You simply need to find which method works best for you. Her is a link to Rockler's set of cabinet scrapers... http://www.rockler.com/product.cfm?page=4898&site=ROCKLER
Besides the scrapers, you will need to purchase a burnishing tool at about $20 - $30. This tool will be used for sharpening your scrapers. Some folks skip the burnishing tool and use a flat head screw driver to curl the burr on the scrapers.
Other folks may chime in on their preferred method of stripping and they will refute what I have just told you. Consider their advise. My method is not for everyone but it sure suits me fine.