Installing original OS on Samsung s3 Is it possible to install Google's original OS without all the manufacturer-added bloatware that comes with the device?

Is there a chance that I would ruin the phone and/or not be able to get it to work as it used to if I don't like it for some reason?

Are there any important features that I would miss out if I had to do so?
You can have some custom ROMs, but if you want just to remove the bloatware, I would just root my device, uninstall those bloatwares and if possible unroot again.

Some rooting methods does permit to unroot and some do not.  Even in latter case all that has happened is just you had rooted your device and still have your original ROM.