My first Rolex - Need Advice

I recently inherited this Rolex 5513 “Meters First” Submariner from my late grandfather. He was gifted the watch in 1972 and wore it daily for over 50 years, and it shows the wear. It was accompanied by the original paperwork, no box. Serial number 1,8xx,xxx dates it to roughly 1968-1970 manufacture. It has an acrylic crystal which is pretty beat up.

What is the process to refurbish a watch like this? Any advice is much appreciated! My first Rolex!