SEO rankings

Hi there, I just launched a Site and I am a bit confused with all SEO-related stuff. I need a reliable, knowledgeable professional to look at my Site and make the necessary changes or give me advice on how to increase the google, bing, yahoo search rankings and what needs to be done to maintain them in the long term. We are a non-for-profit informational website. My website is
www.barbara-stanwyck.com and the keywords are, in order of importance,Barbara Stanwyck, Barbara Stanwyck films and Barbara Stanwyck Biography.

An estimate on what the job will cost will be much appreciated.

Thanks