Personally I would consider sending to Rolex for a service. They will replace the plexi-glass and pressure test the watch as part of the service.
My 1665 has a 6mil serial and has been back for a service twice - they do an excellent job. Once it does get to Rolex they will quote for necessary (deemed critical) & optional work, you could then speak directly to them about what is required and acceptable to your friend. Rolex would replace the bezel & insert at a reasonable price, however that may have been on an exchange basis for me (I was naive thinking that a new bezel insert at £30 was a great idea at the time
)
I have a ceramic Sub also, however I wouldn't look to upgrade from a 1665 to the new ceramic generation if it was a binary choice, but that's my view after wearing the 1665 since '92 & the 114060 since 2015.
Don't rush on this!
