It's an excellent preamp. I owned one years ago. The plating wear is a known problem. New knobs and a new faceplate, from Jadis, will be expensive. If you like the current look I wouldn't worry about it. The problem with non-oem plating is the silkskreening. I don't know of a source. As for tubes, it's a personal taste type of thing.
Try a few and see which you prefer.
Try a few and see which you prefer.