Sizing systems have changed over the years, so '90s garments are often a bit out on modern sizes.
What alteration do you want to make it to it? If it's too big and you want to take the sides in, the method is similar for both skilled and amateur seamstresses so it's unlikely to warrant the additional expense. I would recommend that you ask for the excess fabric not to be cut off though. Most people would do this with an overlocker/serger, with the seam allowance thrown away.