Help with Poncho!!

[wandawoman1167]

Help with my poncho Please!!. Last year I was crocheting a poncho for myself. I crocheted two rectangles and put them together like the baby poncho on the home page here. But I have a problem. I worked for a long time on my lunch hour getting the rectagles the same size. Put them together and it too big and heavy. And the neck hole is too big too. Is there anyway I can fix this? If not how hard is it to undo crocheting that has had the ends weaved in? Sorry, if this seems like stupid questions. But I have never crocheted anything but a forever growing granny square. Thanks.