I have a 2011 Limited with the chevron (?) blinker on the mirror glass. I don't like it. Just wonder if anyone replaced them with the newer Limited mirror housings with built-in blinkers. If so, are the harnesses same on both 2011 and newer Limited (i.e. plug-and-play). Thanks.
I doubt if the harness is the same since your current turn signals plug into the mirror glass and the newer ones like I have on my 2014 Limited are separate modules that attach to the mirror housing ... but they might be.
If the harnesses are not the same, at worst all you would have to do is to tap into the wires leading to the mirror glass and route them to the new turn signal modules. Disconnect (clip if necessary) the signal wires from the mirror glass if you don't want to retain the signals in the glass. If the connectors for the turn signals in the mirror glass won't plug into the newer turn signals, at worst you would have to do a bit of fabrication - maybe with small lengths of insulated wire and connectors from a hardware store.
I see you have a Scion IQ that comes with turn signals in the mirror covers. We have a Prius v wagon that did not come with mirror turn signals. I bought a set of Scion IQ mirror covers and turn signal modules at a discount price from Carson Toyota in California and installed them on our Prius v. It was a lot more work than it will be for you since there were no turn signal wires in the Prius v mirrors so I had to fabricate and run wire harnesses from the Scion IQ mirror signals to connections in the kick panels.
Yours should be a "piece of cake" by comparison. All you need is a set of OEM mirror covers and turn signals from a newer Sienna. Some people like the aftermarket ones from "MIT" (stands for "Made in Taiwan") but I think you are better off with OEM parts since there will be a perfect paint match and you can easily get a replacement if needed.
If you need to fabricate a connection to the new turn signal modules, you can probably find what you need at a hardware store. I used spade connectors from the hardware store when I installed the Scion signals on our Prius rather than trying to buy the correct OEM connectors and it has worked fine for four years. I used machine screws from the hardware store to attach the Scion IQ turn signal modules to the mirror frame - not sure how it will be on your Sienna but you should be able to figure it out.
I posted the part numbers you need in a previous post. You can probably find them by searching for posts from my member name that include the word "mirror", "signals", etc.
This project is probably a "3" on a "1 to 10" scale of difficulty.