See how much you can do on your own; you say you don't think you could handle it alone, but unless you try, you won't know for sure. It's a good way to determine your strengths and capabilities. Once you've got a clear idea of what needs to be done that you can't do yourself, start looking for people to supply the skills you need. The TIGSource boards might be a good place to look for talent.
Bear in mind that you really need to be involved in the development process. If you've got a bunch of concepts but no skills directly applicable to game development - concept art, in-game graphics creation, programming, level design etc. - I suspect you're going to have a harder time putting a team together. It'll probably be easier to attract people if you already have something in progress; it shows that you're genuinely determined to make something, and that you've already put some time and effort in, rather than just having a bunch of ideas with nothing to support them; it's the difference between saying "hey, I've made this, but I need some help, can you help?" and saying "hey, I've got an idea for something I want to make, now make it for me!", which is how approaching people with an idea but no product can easily come off. I've worked (concept art mostly, some in-game graphics) for dev teams where the project leader just spouted scenarios and mechanic ideas and expected everyone else to do the heavy lifting, and it's a nightmare. The team feels used and it can generate a lot of friction, plus the "ideas man", not feeling obliged to follow through once he's got his idea out, can lose interest rather quickly. The last developer I worked for ended up pissing me off so much that I just collected my fee for what I'd already completed and simply stopped replying to his e-mails, and I'm never, ever going to work for a developer like that again.
(If you're after a concept artist, btw, PM me with whatever you've got and I might be interested; it's been awhile since I've done that kind of work, and, despite the tone of the above message, I do kind of miss it sometimes.)