Metacortex

That means the frame was built in March 1970. The bike was most likely assembled a month or so later as a '70 model. You can see the original catalog pages here: Schwinn 1970 Diamond Jubilee -- Krates

In that condition it is probably worth $200 to $300 depending on your local market. A repainted/restored one recently sold for $580 on ebay, but with shipping and ebay fees the seller probably only cleared $450 or less. You should only restore it if it has sentimental value and you wish to save it. You would get the most profit selling it as-is, perhaps with a basic cleanup. If you do clean it be very careful around the decals and the silk-screening on the chainguard, they can easily be damaged.