There are many points of view on the hiring of SEO persons or in doing your own SEO.. Here is my experience:
I hired an expert (whom is highly regarded on SEOChat and other webmaster SEO forums). This person certainly did their job, but never gained me much ground in the search engines. Our contract was such that they had to get me within the top 10 on 3 SE’s within a specified period of time for any of a set of keywords (which were not all that competetive).
The results never materialized. I paid 1/2 the total sum, which I was NOT required to do by contract.
The SEO individual took down all of my sites and confiscated all my content including forum posts.
I had to rebuild my sites from scratch with very old backups (my fault). I also hired an expert to check for backdoors so that this person could not get back in and wreck me.
Be wary. SEO experts, even highly accredited ones, can be very smarmy 