1. If its sill available replace the control knobs.
2.Contact the manufacturer.
3. There are pens that are fine point acrylic paint that you could write them on with manually. There available at Walmart or any craft supplier.
4. Possibly vinyl graphics.
sound like you are on the right track if you have found the screws under the burner caps. some of those types has a big brass nut. some of them you have to remove the unit and access from underneath. send picture of what you are looking at if you like. good luck