You are new to the hobby. So is everyone, at some point, and it's no cause for shame, but it is relevant in your choices. That you are researching and asking questions is to your credit.
Hundreds of new hobbiests come through this forum with the same high hopes that they will be the ones to find the secret to keeping whatever hard-to-keep species and they jump in with cash and enthusiasm and the best of intentions, then burn out and everything is for sale 6 months later because they get frustrated that everything dies.
It's the slow and cautious hobbiests that succeed and survive for a long time in this hobby. I encourage you to be one of them... instead of the ones frustrated to tears when their $1400 frag of Extra-Super-Duper-Multicolor-SPS dies, or just turns brown.
Plans for bigger tanks fall by the wayside. Often! Plan your livestock for the tank you have. They'll work out fine with the bigger tank.
A Moorish Idol is not a borderline fish, not even an advanced fish. It's a fish that has such specialized needs that it's almost impossible to keep in captivity even briefly. Even if a fish is fat and eating, doesn't mean it isn't malnourished and won't suffer poor health and a dramatically reduced lifespan. As Mike said, 1 year is not a long term success.
It would, IMO, be irresponsible of me NOT to tell you how poor the survival rates of this fish are, and it has nothing to do with whether or not I think you would try hard. I don't think anyone would accuse me of being too subtle or slippery when it comes to sharing my opinion.

Now, if you asked the question because you wanted people to give you the answers you wanted to hear, I suggest you add me to your ignore list, because I will never be one of those people!
To put a perspective on my opinion about keeping this fish, *I* wouldn't try to keep this fish. I've kept SW tanks for 13 years, have nursed sick fish for people back from the brink of death, have successfully paired or grouped numerous fish species, and am one of a handful of people in the world to raise the yellow watchman goby in captivity. I am not shy about tackling tougher fish and coral problems.
I wouldn't touch it. Even if I thought I could keep it, I would not encourage the importation of the fish by purchasing one.
As an alternative, you might consider the Heniochus diphreutes -- a butterfly fish that looks like a Moorish Idol but is much easier to keep. Not EASY to keep, but easier. If you have your heart set on one, maybe this fish will be an acceptable substitute.
http://www.fishbase.org/Summary/SpeciesSummary.php?id=7769