It rattles and I want to take it apart so I can fix the rattle. I was able to take the mirror assembly off of the windshield but can't seem to separate the plastic casing pieces. I tried prying in a few spots but it seems that the casing isn't very sturdy so in my attempts, I bent the plastic in a few spots (but still unable to see where the clips are). Thought I'd ask before I do more damage.

 

I doubt the rattle is inside, and it's not a good idea to try taking it apart as there is the risk of breaking the glass and releasing the liquid inside which isn't a good thing.
I'd look at the spring that retains the mirror in the mount, try bending it to tighten it up or get a new one.

 

how do I bend the spring if I can't access the inside? TIA!

 

The spring is in the mount on the windshield. To get to it you only have to remove the mirror, not take it apart. To remove the mirror, disconnect the electrical plug then turn the mirror 90 degrees and pull it off. You'll then see the spring inside the mount.