One click's do not work with gingerbread, the exploit has been fixed. It will be a while before we get anything similar to one clicks.
Nothing breaks by rooting that isn't already broken in stock; i.e. loss of signal bug. By rooting all you are doing is switching the stock recovery kernel out for a custom one "clockworkmod recovery" that allows you to back up/restore/install via zip files. With that ability to install via zips you can flash the superuser app and its associated files. There for the only thing that has changed is your recovery and nothing should break; barring any user error of course.
As for returning to stock it isn't that simple, yet. Right now it consists of flashing a stock kernel via odin that breaks root. It is likely when we get an update or sprint stores get the appropriate odin files, those will be leaked, and we will have the odin method to return to 100% stock.