Yeah it's easy, since the steam version is already patched you just install PR as normal and it works just like that. One thing you need to do though is right click BF2 in your steam Library, and find the option to disable steam in-game, as this causes a punkbuster kick (same in regular BF2).
it took me 8 hours to figure out how to get it to work on steam. all i had to do was uncheck the steam ingame in options. DO NOT FORGET THAT. you will be kicked from online every time.