I said a year but I've reconsidered. A week or a month would probably be good. Depends on what happens to my life though. It's not like I could lead my old life as the opposite gender all of a sudden one day. It would have to be separate somehow. Like a timeout from my real life.
I don't know why makeup, clothes, fashion, jewelry, shoes and the like have to be a big deal. Girls don't have to follow that type of lifestyle. I actually like girls who don't bother too much with all those excesses. I take care of myself already and I figure it wouldn't be that much different as a girl. Add a little makeup (not much because it seems like way more of a hassle than it's worth) and more shaving, that's about it as far as appearance goes.
I don't think it'd be more difficult than being a guy. There are advantages and disadvantages, tradeoffs.