What really happens on a service for a vintage Rolex?

[ReclinerTimer]

So like many of you I am a watch enthusiast, but am young and just got into the hobby a few years ago and have just one Rolex. It is a late 70's early 80's stainless steel smooth bezel Datejust. I have never sent a watch to Rolex, but plan to for this watch when it's time for a service. I'm just wondering, what does a general service entail for a vintage(ish) watch. Along with a basic cleaning, what really should I expect they will do? Replace parts of the movement? Replace the dial, hands, or minute markers? Do something random to the bezel or bracelet? Please help a newbie out :)