When I looked at the picture of your bike, the first thing I thought was that it is too big for you. The second thing was that this is a really clean, but very low end, bike. I would guess it could be made into a very dependable bike for very little money but you can't fix fit so it would be a waste of time and money.
I agree with getting the GT (or something similar) but resist the urge to upgrade it. Keep it well maintained, replace things if they break and keep putting money away for your next bike.