My wife used to do that. One time, she took it to the shop and spent $600. The second time, I overruled her. I ordered a replacement mirror for our van on line. I then spent an afternoon taking apart the passenger door. I found the three screws, and after banging my knuckles a few times, figured out how to remove them. I then put the new mirror in. Even though I had a few screws left over, it works great.
It is a one hour job if you know what you are doing. A two hour job if you have a good instruction book. An all day job if you were working blind like I was. Oh by the way, the new mirror cost $80.