The rear balance pieces will be installed OVER the existing rear bumper. In order for it to look good, it will have to be molded to the rear bumper. Same goes with the side skirts, they need to be molded if not it will look really messed up. As far as the front, the front bumper reinforcement will not fit unless it's modified. The easiest thing that the bodyshop will try to do is remove it all together. Then if you get into a merely 10-15mph fender bender, you can kiss your nose goodbye. The only other option is to trim the bumper reinforcement to fit the front bumper.
I would definitely not try this on my own. Erebuni's kits are known to NOT fit properly. So unless you're good with fiberglass and have the necessary tools, I wouldn't even look at it for too long.
Have a nice day.