I think the TX2 arrives with R27.0.1 installed, but you’ll definitely want to flash with R27.1 before working with it. You can use JetPack run from an Ubuntu host to do this. See:
You might optionally consider getting set up for serial port access if you think you might need to do debugging (serial console works even when video and networking does not). See:
…the TX1 uses the same carrier and serial console as the TX2. The part you may not have on hand is the USB serial UART and the connector.
If you are using a local/native display make sure it supports HDMI (HDMI to 15-pin D-sub adapters do not work).
Since it is a computer, there is the always-needed surge protector if you want to be cautious.
Bookmark this page for documents (you’ll need to have the free login to download most docs):