Hi cwg, welcome to these site,
Here is are step on to replace the towing side mirror. Hope this may help.
First remove the door panel and once the door panel is removed you'll see three nuts and the wiring connector.
Next step Unplug the connector , and remove the 3 nuts , being careful not to drop them into the door. Don't worry if you don't have help holding the mirror while you do this , because they will not fall off.
Once the nuts are removed go to the outside of the door and gently , but firmly wiggle the mirror out and install the new one , tighten snugly and reconnect the wiring plug .
Then check your turn signal and parking light to be sure it works correctly . Snap the panel back on , and do the same to the other side .