How can I change my personality?

Okay, please don't say that it can't be done or anything like that, because I honestly need to change my personality.

I'm a sixteen year old girl, by the way.

Here's the deal, I'm a very shy and introverted person. However, all the things I hope to accomplish in my life kind of require me to be a little more of a go-getter. I'd like to go into business administration, marketing, or ownership. But, that requires talking to people, running meetings, and things like that.

I also am a bit of a weird girl, and I don't really care that much about fashion...I mean, I shower every day and dress appropriately, but I'm never all that up to par with what people assume a girl should look like, and shopping for more than two hours bores me to tears.

In addition, I'm somewhat lazy. This I'm taking care of by just signing up for things--I've signed up for a gym and extra dance classes, so that I have an obligation to get off my butt and do something productive. I can't stand to break obligations so I figured this will work spectacularly.

I figure a lot of it is just deciding what I have to do. Actually go shopping and try to care about the necklaces and shoes; just start talking to people; and things like that. But, if there are any tips or articles that would help I'd be much obliged.