noob question but does it stay in questing area?can it quest again? does it return to hand? cheers

Using the ability of a quest will only affect the unit on the quest if that is specified in the quest's ability. For example 'Journey to the Gate' states that you sacrifice the questing unit when the ability is used. A quest like 'Wolves of the North' or 'Offering to Hekatari' does not state that anything happens to the unit when you use the quest so it remains in play on the quest.

TL

The unit can only be placed onto quest from the hand and you cannot place it on a quest that already has another unit.

After that while the unit remains in the quest zone it is questing and the text of the quest should be consulted for what should happen to it - there is no implicit rule for that.

If the text of the quest orders the unit to be sacrificed to achieve the quest, then the unit goes to the graveyard. If the quest does not instruct you to sacrifice the unit and only asks to spend accumulated resource tokens, then the unit stays on the quest and is still questing - so next turn you will be able to put a new resource token on the quest.

But as pointed out by Vitamin T some of the quests do not have a clear state when they can be considered "complete". For instance "Wolves of the North" allows questing unit to attack right from the quest zone; it does not cause any resource tokens to be placed on the quest - the unit just stays questing and nothing happens to it.

If a unit, like Pistoliers, is moved out of the quest zone, it is no longer "questing". Note that when a unit leaves quest (either by changing zone, or getting killed, or due to being sarificed) all the tokens from the quest are discarded, but the quest itself remains in the quest zone.

Oh, and of course questing units contribute their power to the number of cards that you draw, and can defend your quest zone.