Replacing a nut and filing it decently can be one of the trickier aspects of a routine setup or, put another way, quite easy to foul up and ruin the action or introduce fret buzz.
Getting the old nut off may turn into a pig. Filing the slots to the correct gauge and depth requires tools. There is a welding tool that can provide the correct gauges cheaply. Warman sell one:
http://www.ebay.co.uk/itm/Guitar-top-nut-file-tool-set-with-FREE-UK-P-P-/160987242032?pt=UK_Guitar_Accessories&hash=item257b965e30
and a similar thang is on ebayUS:
http://www.ebay.com/itm/Cigar-Box-Guitar-Tools-Long-shaft-Nut-Bridge-File-Set-40-01-01-/181108298885?pt=Guitar_Accessories&hash=item2a2ae55485
but, as Warman say, they’re not guitar pro files and only good for plastic nuts. No use for bassists, unfortunately 🙁 . Normally, I’d say “give it a go, good to learn, buy some plastic nuts and the welder’s tool” but you’re talking about a Graphtech on a PRS. I say “take the Graphtech + PRS to a luthier/tech who won’t actually charge you very much, has the proper – £60+ – files and won’t hash it up and ruin your action.”
EDIT: As for whether it’s worth doing. I’m usually fine with a boggo plastic nut but I’m cheap and better players on Talkbass hate them and fit bone, graphite, brass, YMMV anything but plastic. I do have the graphite/PTFE bridge saddles on my piezo-equipped Jazz and they are jolly nice. I would imagine, if you dive that whammy a bit, that they’ll save you on string snaps. After all that, though, I’d be surprised if a $2000 PRS has some POS nut in the 1st place ❓