Is it difficult for a so so mech to replace a side view mirror on 03 Toyota Highlander.??
Maybe, maybe not. I’ve replaced two, one on a Camry and one on a Civic, and they typically attach with three bolts of about 12mm. On the inside is a pop-on trangular plastic trim piece called a “garnish”.
The problem is that on some cars the inner door panel needs to be removed to access the bottom bolts and that can complicate the job unless you’ve removed door panels before.
Pop off the garnish and you should be able to get a feel for the project.