Changes in a Flash website

Hi, We have a ready flash website bought of a template website. We did some changes in the xml which turn out fine and the images we have changed too. However it's the flash part we're strugling with. The background sound has to be changed, we tried to do this already but then the xml doesn't seem to work anymore. We also notice that the site loads much slower when we have done that changement, the swf file is also 3 times bigger. We need someone who's expierienced with flash and can do this tiny job. Thank You