Vintage Datejust/Oyster Perpetual Question!

[ramonesf2]

So I've been looking into vintage Rolex, specifically Datejust (or Oyster Perpetual Date/No-Date) models. I don't really know what to look for in terms of model years and reference numbers. I know the older models do not have quick set date, but I don't know what year that changed. I'm looking in the $2k range for a Datejust in good condition. Is that a reasonable price range, or am I dreaming? Any help is appreciated! Thanks!

I'm not too concerned with box and papers because I'm not purchasing it to sell in the future. I plan on wearing it often and am not too concerned with preserving value. As long as it is in good mechanical and cosmetic condition, I'd be satisfied. Also, I'd prefer 36mm.

Bonus: If it is from 1966. Special year in my personal life.