under shield holding damaged
 

I found that the left rear end of front undersheild pastic sheet bent down and is loose.

I thought the bolt was not tightened, but it seems that the metal part into which bolt goes has been detached from the body.

Is it expensive to repair this?

If it the similar to those on my '87 300TD, they are rather simple bolt retainers that snap into receiver holes. I believe the holes are actually rectangular. Not certain, but they certainly don't appear as if they would be expensive to purchase and they are a breeze to install.

Someone else more familiar with your model may be able to correct me if I'm wrong.