craftgrrl | Sweater Tailoring Question

I have a sweater that's a bit too big, and quite honestly a little frumpy... I LOVE LOVE LOVE it though... and I want to make it look better by fitting it a little... So, If I wanted to cut a section of a sweater with a wider weave, could I do that? If so, how? I do a lot of other sewing and crafting, but the art of making sweaters eludes me. I'd love to think that I could just pin a taper, stitch it, and surge the edges...like I would with fabric... but this sweater I'd like to change is just too darn expensive to mess with if it's not going to be done right, y'know?

Here's a pic of the sweater: