If your wood has never had anything on it, using a stripper is overkill. It simply needs a good wash with a product that will kill any mold/mildew spores (you can't see them but they're there!!) You can brighten to give the wood a more even look prior to staining.

Here is a link that might be useful: Step by Step Instructions for Prepping Wood

Carolina, thanks for the link. So, from that site, would I need the EFC-38 (cleaner/stripper) followed by oxalic acid (wood bleach) rinse, or just the oxalic?

EFC-38 mixed at the least measure would work well for you followed by the Citralic product. Citralic is a balanced blend of oxalic acid and citric acid - little safer for the user and easier on the wood. It will neutralize the ingredients in the EFC-38 and give your wood a nice even tone for staining.