If your mirrors are not dented or overly destroyed, you can restore them like I did.
After you remove the mirror lenses and rubber backing, take the stainless mirror pods off of the arms. The arm assembly is made up of materials which don't rust, I cleaned mine with CLR and fine steel wool on the chrome parts, and then polished them with regular motor oil.
The pods have a bracket inside which rusts because it is steel, and you get rust streaks on the outside of the mirror, etc. This I remade by hand from 14 ga stainless, and bolted it back on instead of the rivets they used.
I then buffed the mirror pods by first using a cut polish to remove all the scratches, and then a finishing polish to give it that nice chrome like shine. There's even another finer polish, but I didn't see the point of doing it because I got mine looking pretty stellar if I may say so.
Anyhow, pics are worth a thousand words. Here you go: