...quest. what lvl do u have to be? what city and where

What epic mount quest? There is no quest. Just go to the riding master / flight trainer when you are the appropriate level (40 or 70, depending on ground or flying mount) and buy the skill.

What epic mount? there is none for any class really. only class mounts i can think of are dk's, pally's, warlocks.

The basic level to get epic ground mount riding is level 40. You purchase the training from the riding trainers found in any major city, then you have to buy the mount itself from your own type of faction.

Only Death Knights, Warlocks, and Paladins receive their mounts/training for free, as they either have or had quests you were forced to do in order to get their special class mount.