Second I do not use Macs for very specific reasons such as these, but I don't think any of these programs to root and unroot work with Mac. Do you not have something like boot camp installed so you could dual boot into a Windows machine for applications that won't run with Mac.
I would do a search on here, I would do it for you but I am on my phone. How did you root in the first place? Did that method not have an option for unroot?
I rooted it here from a video on youtube. His videos were removed recently so i never had the chance to get the unroot video. I never got around to installing bootcamp i think i might call up my cousin near by and use his laptop. and invest in bootcamp and what not. I know its free but the windows product isn't. I tried to update it to the new ICS program but it wouldnt update. My brothers whose phone is also rooted was able to update it yesterday but i had no such luck.