As far as the crank & seal . If you had replaced the seal , I agree , I would spray the crank with PB Blaster , then use either very fine grit sandpaper / emery cloth ( or very fine steel wool ) on the rust . Spray then clean as many times as you feel is needed .

However , if it were me , I would go by the saying , " If it ain't broke , do not fix it . "

God bless