Up to you.....you have a buffer being the edge. So you could sand the exterior and sides and just paint them for now.
But, if you are doing it.....why not do it all at once. The paint on there looks pretty thin, so doubt it would take too much effort to get it of the internal side.
But, if you are doing it.....why not do it all at once. The paint on there looks pretty thin, so doubt it would take too much effort to get it of the internal side.