From what I’ve been able to learn on one of the Toyota Owner’s forums, this “should” just be a software update only, meaning that if your 2018 Camry or Sienna already has the required hardware/software, it’s a simple matter of just downloading the software update from the Toyota website (see below for the link), copying the software update to a USB flash drive formatted as FAT32, and installing the software update via the USB port in your vehicle. There are instructions on the site for how to do this, if you've never done a software update on your vehicle before. Which means you won’t necessarily have to bring your car in for a service appointment and possibly incur any dealer/labor charges.
Also, the software update will not be available for download until at least Monday, May 6th. I will update this thread once I have downloaded/installed the software update to let you know whether or not I was successful. I will be installing the software on a 2018 Toyota Camry XSE with Entune Audio 3.0 Plus. Here is the link to the Toyota download site:
https://securedp.toyota.com/download-app/getUpdates
YMMV (see what I did there?

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