Thank you for following up.
Plz let us know how it goes...

Add- in the sprit of fun and craziness, if anyone wants to reverse engineer a way to do a standard off the shelf double din installation and document it and share the results I'm in and will help and hopefully others will too.

I think it can be done for some years by the right person willing to try. Like Salim and others say above there is more than one radio available(nak vs non-nak) and a Nav option too to make things more complicated but that's ok. Amp bypass will need to be done for speakers but amp will need to stay plugged in and functioning for NAV and camera to continue working.

Of course this assumes a double din would fit by removing just the old radio only so hopefully someone can confirm that. Otherwise it may be a single din. RX330 radio removal leaves a double din hole in the dash but not 100% sure if this is so on the RX300.

Edit- after looking at the wiring detail more closely it would probably be easier to do 2 threads- one for Nav and one for non-Nav.