I started leveling a Priest today and i intend to heal at 80 (holy or disc, whatever is needed and whatever i prefer) but im wondering what would be a good level to switch from Shadow to a healing spec to get enough experience to be decent at 80. I'm level 20 at the moment and i've never healed before, i've always tanked or been dps. Also i'll run as much random dungeons as i can while leveling.