There are several people that post here and on Gaydemon.biz who have good knowledge of SEO. All of them say that hiring an SEO guru is pretty much never worthwhile, because the ones that don't know what they are doing can get you permanently banned from search engines, and the ones that are really good are (a) impossible to find and (b) incredibly expensive.

There have been several SEO workshops on various boards (including, I think, this one) and many of the knowledgeable people will help you out for free if you ask nicely