Well, hmmm. If this is one of your first sites I think I would try and find a few different keyword phrases, to see if you can somehow narrow your results down some more. That's an awful lot of competition, if your not right up on SEO and also
continiously building your seo campaign. This is not to say that you can't do it. One of my sites has around 38,000,000 competing sites overall and I am steadily climbing and am showing up on pages 2 and 3 etc. now for some of my terms.
You see although when you type in qoutes, and get 91,000 in return, this means that, these sites are in direct competition for your keyword phrase. Now just because these other sites may not be using this exact search term, they can still easily outweigh you in the results. If they have a lot of quality sites linking back to them, the number of links coming back to them, thier site structure, site optimization etc. will have an important role in this factor.
I would try and find a way, especially for your first site or two a niche that has preferably less than a million competitors, or at the very most 2 million.
Lots of competition is usually a good indicator that this is a popular subject and there is money to be made

So I'm not saying don't do it, but be prepared for more work and delayed results.
At present I'm working on a site all about SEO, with this forum in mind to help some of the people hopefully from the start of their site building, so as to save them, much of the restructuring and extra work I had to do.
I have learned the hard way, that building and optimizing your site right from page one, and every other page, right at the start of your building, and preparing it for your competition, saves so much work in the long run. It will be introduced soon, but I have a few more things that I want to get done with it yet.
cheers Davin