Whether clear or white, I would paint it. Every bit of wood that is coated leaves less to absorb moisture or otherwise deteriorate as it ages. However, I would leave the outside as is if original. I'm of the every scratch and nick tells the story of it's life, (ok, maybe that's a little dramatic) but unless the cabinet paint is trashed, like to do a good clean, light touch up, and wax.

Oops, sorry didn’t realize outside wasn’t original. Have fun painting, look forward to seeing the end result.