It may seem easy to throw some money at an "SEO firm", but it's really difficult to find anyone that will give the kind of care to your Internet marketing as you would yourself.
Assuming you have designed your web pages with SEO in mind (proper title tags, h1/h2 tags, reasonable keyword density), then the major challenge will be getting quality inbound links.
But that doesn't have to be so much of a challenge. While many SEO firms may charge hundreds of dollars per month, I have achieved PR5 and 1st page Google ranking by purchasing 5-10 inbound links from other quality websites.
In other words, I highly suggest educating yourself first, and doing the SEO work yourself.