I was browned off buying an expensive car and finding a lot of the body exterior made of plastic, but there are three reasons why plastic is used:
1. Safer on impact during collisions. Other parts of the car absorb the impact. If you hit a pedestrian, bodily damage will be less significant in minor collisions.
2. Cheaper and easier to replace and manufacture.
Removing the front fender to replace grills is of course possible at home, but you need the car jacked for easy access to the screws which hold the plastic parts in place, and the right tools. I have a Bentley Publishers X5 e53 manual for my car. Recommended. It will show you how to remove and replace everything on the x5, including even buttons on the instrument cluster. Removing front grill is too complex to explain in words and would be better served with the aid of pictures, which manuals do provide.