I have been playing wow for a few months, made it to lvl 40 on a MarksHunter, and then realized, all the time i used to make it was a waste, cause i did't even enjoy it.
This led me to roll priest about 2 weeks ago, and I've always loved to be the healer of a group in many different games, simply because if i play my role well, i ussually get the most praise. So, i started spending my points in holy. And I'm not half bad, although only lvl 28 so far. But, although i love to do an instance or 12 a day, i also love to just go out and quest awhile. Being holy specced ive already felt the effects of being dependant on someone else doing the damage, and now i wish i would have fed my pet more as a hunter, cause god knows Static the Raptor deserved it.
Is there anything i can do to be able to go out and quest, without having to respec?
If not, is it worth respeccing simply to go out and quest, leveling in that manner, or should i keep grinding instances?
I've already respecced once to shadow, but i didnt get the same feeling i like to have in holy spec.

There have been many discussions on this forumm on how to level as a priest -> check then out for reference.

I do not think respeccing is essential at this moment. However, you better should start picking some talents from the disc tree. As a holy priest you will gain survivability by picking disch talents. Personally I would start with wand specialisation. In many cases you will start with a certain spell rotation and at (let's say 20% health) wand your opponents down. Obviously you will need a good wand equipped too :-).

Levelling as a holy priest my be a little bit slower out of instances, but it should not be any problem.
Have fun!

Agreed with the above poster.  Even if you intend to heal, no priest is complete without skills from Discipline.  It is certainly NOT worth the cost to respec at level 28, unless you have just been spending your points absolutely terribly.  Chances are that you can recover to a decent leveling spec in about 5-10 levels by dropping some points in the right spot in Discipline.

Speaking of which, I have posted variations on a theme of Holy/Disc leveling specs in the Priest forums before, so I'd advise to go look at those threads and read about the specs in context, or you can post your current spec and we can collaborate on a way to fix it without requiring a respec so that you can level easier.