I would say that it's not a good idea to try a Disk Utility repair of a system that is newer than the version of Disk Utility.
Here's a method that you can always use (and does not need to boot to another disk at all)
Boot into single-user mode: restart, while holding Command-S
You'll get a screen with text scrolling down. It will stop at a prompt.
At that prompt, type: fsck -fy
then press enter. You'll see several lines showing that various disk tests are running.
If that test ends in some kind of error, run that same fsck -fy again, until no problems are found.
If you get the same errors, and continue to get the same errors 2 more times, then you would need to run a more capable disk repair.
I recommend Disk Warrior.
That being said - why do you need to run a disk repair? What problems are you experiencing now?
And then, If you do need a Snow Leopard installer, you can get that directly from Apple. It's only $20...
Here's the Apple store page for that:
http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard