Personally mate Id use this guide:
Just remember once you root you wont be able to update your phone. You'll need to unroot it first.
I'll be having my GN2 in the next few days and really want to root it but as you I want to keep the stock rom. All the phones Ive had in the past Ive used custom roms on but would like to keep my new GN2 stock for some time.
Let me know how you get on