Welcome to the board, aaronjf. You can check out the charter and post a "Help Wanted" request in our Commercial Exchange [webmasterworld.com], which is provided for exactly that purpose.
Meantime, since this is the ecommerce forum, it's a good place to look at some of the things to keep in mind when doing a commercial site selling products from the ground up.
>trying to find a reputable reasonably priced SEO company
For one thing, if someone is doing a huge ecommerce site that needs to be database driven, their requirements are more than one that's got 40 products and is a neighborhood store. The cost will be completely different for the two. One may need an SEO who's capable of large Fortune 500 sites, the other won't; and different companies have different rate scales according to the type of sites they generally work with. It's the same as with web designers. Some won't look at a job for less than $5k, others charge $10 an hour. Somewhere in between is usually where the need will be met, with the appropriate skill-set for the job.
>more importantly how do I know who is good and who is below par?
You've landed in just the right place here at WebmasterWorld. You can know by reading for a bit. There are only so many basics involved in optimization and you'll find plenty of information here to help you learn enough to be able to make your choice.
If you read through the submission forum you'll find out that automated submission to hundreds or thousands of search engines is misleading and unncessary. You'll find out that those who say "we do custom meta tags so you can be found and rank high on search engines" are equally wrong. Some offer to set people up in the types of links programs that could seriously jeopardize their sites. Half the battle is knowing what to avoid in the first place; it's all here.
For a modest-sized ecommerce site, it's easy to make sure the site will be spiderable and easy to get rankings for if it's done along with the original development. Keep products on static HTML pages and link to the shopping cart. Make provision in the design for enough text on pages so that search engines have what to work with. Pick the keywords that people will be looking for and use them in the right places. Do the navigation to be search-engine and user friendly. Choose reciprocal links carefully.
What's basically different about setting up a site selling products is that for search engine purposes you'll want to set up the sections for product categories and individual pages to target keyword phrases that shoppers will be searching for.
The up-side is that what makes for an easy to use and navigate site for visitors is generally also search engine friendly. Keeping it simple and staying away from fancy tricks is generally the best route to follow.