For coverage reasons, I'd like to deploy 2 wireless access points for my LAN.
Do I just plug both AP's in to the same wired lan, and set them both to the same SSID & PSK? (On different channels, obviously.)
Yes sure, You can use two Access Points for same LAN. two ways you can use these access points to your network.
Either attach Access Points with LAN cable directly to Wireless LAN port or also you can attach one LAN cable from Wireless Router to Network Switch and you can attach your Access Points to your Network Switch.
Attaching to Network Switch would be more accurate and better way to perfom.