Prius (2010-12) :: Grinding Noise Near The Front Axle

So I was driving yesterday and I hear a grinding noise near the front axle. I pull over and a plastic panel is hanging off near the front of the car. I go to the family mechanic to have him put it back on, and since one of the clips are missing, he tells me to go to the dealer to get a clip and have them fasten the panel.

This morning I go to the dealership. The service advisor gets me right on a lift and comes back about 20 minutes later with a slip of paper. He tells me that the piece is the door from the under body plastic protection that protects the oil reservoir. There are no sides of it that seem to have been ripped off a larger piece, just holes to be screwed in. He tells me the whole entire piece needs to be replaced, end of story. He did not offer warranty coverage (I have 20K on the car) and was not interested in speaking to me further on the topic. The parts desk pulled up a diagram of the car and showed me the panel as part of one big piece underneath that needs to be replaced.

I am going to seek out another dealership on this, but I wanted to pose this to you all as well. First, do I even need to replace this small piece of thin plastic? Second, if I do, can I buy just this small piece and not the entire under body panel. I noticed some threads about the poor design of the oil door, and perhaps this is what this is? I do not have access to a floor jack or garage, so all of my service (free toyota care) has been done at this specific dealership. Here is a pic of the piece.