Welcome! I would start by taking some time and reading the forums.. You'll see terrible stories, but you'll also see good ones. It's no secret the EcoDiesel has it's issues, but the best you can do is learn to help extend it's life. Keep us updated and ask any questions you might have!
It'll warn you when it's low... if you have no check engine lights/etc drive it. But, if it's been more then 3 or 5K miles, I would add a 2.5 gallon jug to see if it responds.