Help required -- deleted system/wheel from sharing and permissions

Question

So I just did a big clean up on my hard drive of old files, and wanted to see how much space I now have left on my HD - I right-clicked on Macintosh HD > Get Info.
Under Sharing & Permissions I noticed a strange User listed named "wheels".  Afraid that someone had accessed my computer or was somehow sharing on my network, I went ahead like an idiot and deleted the "wheels" user without first researching what it was all about.
Now I cannot boot, nor can I reinstall my OS because it says permission is denied. 
I really don't know what to do at this point, I am hoping that there is a command in terminal that can undo deleting wheel/system. 
I would very much appreciate the assistance, i'm starting to go a little batty.
Thank you

Answer 1

I just did the same thing and went to the Apple store to talk to the geniuses.  I don't see any updates to your post but hopefully you were able to figure it out.  Just in case and for future people who do the same thing, force power off the computer. Power back on while holding down the option key.  In Mountain Lion, this should now give you a screen with your main hard drive and a small partition that contains a backup of the OS.  There is also a network dropdown and you should log in so you have internet access.  Then select the OS backup partition and essentially reinstall the operating system.  The reinstall should keep everything on your hard drive intact just like if you were upgrading the OS from an old version.
Hope this helps other people