It's easy. All you need is a thin butterknife from your kitchen.
There are (IIRC) three plastic slide-in tabs on the top of the assembly, and two plastic clips on the bottom of the assembly. These are what hold it into the visor assembly.
First, pry it up slightly at the bottom to locate the two plastic clips. Then use the butterknife to press up from underneath each clip, while gently pulling the mirror up out of the visor. Do one first, and then when you do the second one the mirror will be free on the bottom. When you have it free on the bottom, just pull it down and it will come completely free. There are no wires or anything to mess with, that's all you have to do.
When putting the new one in, just slide the tops tabs into their position and then firmly press the bottom of the mirror down into the visor assembly. You will hear two clicks when the plastic clips catch.
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