It could be the neck, nut, saddle, bridge or even the soundboard/bracing, or a combination, that's causing the high action. Best to post some pics of the guitar first so the possible cause(s) can be assessed before embarking on a course of action. Pictures of the action at the nut/1st fret, the 12th fret, side on of the bridge/saddle, and of anything that looks bowed or out of shape is probably the best place to start.