Question about heated mirrors

Okay, so I would really like to have the heated mirrors from a Limited on my 05 SR5. My tundra has them and it's really handy. How easy is it to swap them out (electrically speaking)? Plug and play? Then, as I understand it, on 4th gens they are wired together with the rear defroster which opens another can of worms. I don't want to use the rear defroster for fear of shattering the rear glass but I don't want to totally disable it either. On occasion I will sometimes turn it on for just a few minutes to help get the frost off the glass. I have a method to this. When I turn it on I think of a location a few miles ahead and make a note to turn it off when I get there. That way the glass gets just enough heat that the wiper/washer can clean it off but not enough to blow the glass. How can I overcome this? I thought about wiring the mirrors to a separate switch but then I'd lose the timer function. Also thought about putting a resistor in the circuit to the back glass. Hopefully that would keep it from exploding but maybe send enough current to help with clearing the glass. Anyone have any suggestions on this? (I used the search function but could find nothing to help me).
Hmmmm, as I was re-reading this before posting I thought of another possibility. I could possibly wire in a lighted toggle switch for the back glass so I could basically keep it off at all times unless I wanted to do my 2-3 minute routine on it. Sorry for the long post. Any ideas appreciated.