Hello Slipperman,
I'm a graphic designer and have done many logos. A few important things;
Yes, make sure it is a vector logo with a transparent background. EPS with text to outlines.
Using any stock image will usually nullify you ever trademarking or registering the image unless you get an extended license.
Make sure the logo can work as a one-color (We start logos this way and ad color after) for watermarks, shirts, coffee mugs, etc.
Make sure it can work when small, as in banner ads, etc for the internet.
99 Designs can be OK, but, you really need to define the job well. MAKE SURE YOU GET A VECTOR EPS image. Or a very high resolution PSD file. We find some great artists there, but, they can be somewhat inexperienced to the big picture.
Freelancers can be an inexpensive way to go, but, remember, freelancers often do not stay around long, and you may need support down the road only to find they are no longer available. Be careful, we have often had to redo a logo to fit in a particular situation and the originating artist is gone. And you may need support for other collateral pieces like business cards, stationary, marketing pieces, internet and so on.
Logo design/Corporate identity is an art. Stay clear of fads and do something that will look great 20 years from now. I generally am hesitant about one doing their own logo, but, rules can be broken. And as I often have said, it is not what you want, but, what your customers want. Identify your demographics and put yourself into their frame of mind.
Hope this helps,
Brian