Yes, others have worked on the course. When the Diamondhead Company owned the course in the 70s they removed the sandy scrub rough areas and planted wall to wall grass. After ownership changed hands the sandy areas were thankfully restored. Nicklaus' outfit I believe resurfaced the greens several years ago (Bermuda to bent I believe). There were some wild stories about the process that I'm skeptical of. Rees Jones was brought in by the USGA to tidy up things, and it did appear he messed with some of the bunkers' shapes. They didn't have the same look they previously had. I have no idea what C&C have done...and it doesn't appear you know either.
There have been no major changes to the course Ross left that I'm aware of, which is rare for a course of its vintage, especially one that has hosted major championships. Yes, I would prefer Rees Jones, C&C and other architect would leave it alone.