Congratulations, welcome to the family (so to speak).
Check here: http://www.xbox.com/en-US/support/hardware/memoryupdate/default.htm that will help you with the upgrade to the NXE. I didn't mind the blades at all but the NXE is a slick interface.
If you like JRPG's, Lost Odyssey is really old-school and absolutely enjoyable. WRPG wise I'd recommend Mass Effect.
Is Culdcept Saga multi-plat? I don't know, but that was a fun game.
Finally, if you plug your 360 into the net for the NXE update, and then disconnect from the net, you never have to worry about a game needing an update, as your box will never know there is one out there...
Hope you enjoy it. I'm getting a PS3 eventually, so I'll join you in your multi-console enjoyment!