Ryan, SEO services are one of those esoteric services where you can get out of it what you put in to it. If the service is a hundred bucks a month, with 99% certainty I can tell you it's not worth it. If it's $300/month, or a fixed fee service, then it becomes a matter of vetting the person or company and understanding what's included.
Regarding your site, it definitely needs much of what would constitute a standard SEO punch list. From basic SEO devices, ramping up localized content and tags, to getting a consistent use of a Name/Address/Phone on your site that matches up with any off-site citations and local accounts. For example, your Google Places page has an address, whereas your site has nothing but your phone number. It helps to have all instances the exact same, and most importantly, to have it the same on your own web site. Consider this a corroboration of your business, and site's, legitimacy.
If you want to have a better understanding of the concepts, read the past reviews here or search for Google and seomoz's respective beginners guides to SEO. I've linked those quite a bit here, and they are a great intro.
Questions or clarifications, just yell.
a guy who knows both the lawn business and web strategy