It's kind to Production not to surprise them.
Leave the reference designators as R1, R2, R3 etc. That won't confuse anyone building the board by hand, or programming a P&P machine.
By all means annotate your schematic to say what each one does, if it's not obvious. I'm surprised how few schematics are marked up with notes as to why things are done a particular way; I do it all the time to indicate nominal voltages, the meanings of hardware revision bits, the meanings of the signals available on test points, and so on.
Also consider putting notes on the silk screen of the PCB, even if it's just "GAIN SET" and a box around the parts which are relevant.
If certain parts are likely to be changed frequently - perhaps during development, or to customise a design for different applications, then consider using a larger size for them. For example, I have a design which is mostly built using 0402 passives, but a couple of resistors are 0603 because they're easier to rework, and the part is marked with the value.