No and no. No, it won't make a difference to your appearance until you lose weight. No, you should bother with abdominal (and other) exercises. I'll explain.
Envisage your stomach as two layers. Layer one (the bottom layer) is muscle - your abdominals. Layer two (the top layer) is fat.
Initially layer one is extremely thin, because we don't naturally have well defined abdominal muscles. By doing certain abdominal exercises, you can stimulate layer one to increase in size. Now essentially you could make layer one as large as you like, but if layer 2 is covering it up (ie. the fat) - you're not going to see a single thing. It is essentially a blanketing effect.
Consider the two photo's below taken during my transformation:
In both photo's I have a very similar amount of muscle mass (as I had been lifting weights prior to the first photo for a while). The big difference is the amount of fat I am carrying. On the left you can see that I have a layer of fat covering up my midsection. As a result, you can't see too much in the way of abs. Strip all that fat away and you get the photo on the right.
The reason why I suggest that you do perform resistance training is twofold. Firstly, it will encourage muscle growth which will assist fat loss by speeding up your metabolism. Secondly, once you do eventually lose the fat, there will be some good looking muscles already there! It takes a long time to build muscle compared to losing fat. Start now so you can build some solid foundations for the long-term.
It should also be noted that females will not experience nearly the same effect from weight lifting that males will. So, by performing abdominal exercises you cannot expect to obtain the definition in the abdominal muscles that I have. Females will tend to see more of a 'toned' effect.