I am a little confused, do you need to buy your ridding skill to ride the Felsteads? :?
Nope! you get both riding level 75 and 150 (the regular ground and the epic ground) training when you complete the quest and get the spell to summon each!
Little update here, you no longer have to complete the quests to learn the spells. They are purchasable from the trainer at the appropriate level.