Peel the face sheet off side to side not up and down. Sand it down starting with an 80 grit and going through the grits to a 220, then give it a good oil. It doesn't look like it's seen any linseed at all. Couple of coats and then wait a week or so if you're going to put a new face sheet on.
From the pictures I would leave it well alone. You risk doing more harm than good if it's still playing and sounds alright. Take the added tape off and re-apply some new over the right areas.
And what do you then do if it gets worse?? Prevention is the best cure...