Daniel, you will need to remove the old finish first, by sanding, or chem stripper, I prefer to sand. I usually start with 120-220gt on a random orbit sander, then by hand 320-600gt. Any oil based stain should be fine, water based has a muddy look to it, to me. For a sealer I prefer to use either Teak oil, Tru-oil, or a spray on poly. HTH and if you have anymore ?'s just ask. Also be sure to post a pic when your through.
Mike