Some a--hole knocked my driver side mirror last night in manhattan. The shell is fine but the actual mirror shattered and is hanging by a wire. I see the replacement glass on pelican for around $60. Is it easy to install? Do I need special screw or additional parts?

 

You don't really need any tools at all. Maybe a small screwdriver to help prise off the old mirror.
The new glass has the fixing bracket attached to the rear and simply pushes on.