Something to keep in mind is that every map, no matter what scale, no matter what theme, is wrong. Every single map. But you have the recipe for success: Being able to cross-reference multiple resources.

Recommended reading: Monmonier's "How To Lie With Maps"

Also, some public-use maps are intentionally less-than-correct (by omission) in order to protect archeological resources, let over-used areas and trails recover, etc... With this in mind, never get rid of an older edition map.