What a nice survivor! I'll take a stab and date this right around 1963--if I'm not mistaken, 1964 and later had a different, more angular tank. Does it actually say "JC Higgins" on any of the badges? I get the impression this bike is from the post-Higgins era, when Flightliners were simply badged as "Sears."
As to value, these bikes aren't that uncommon, but MAN is that a beautiful cache of documentation & spares. They definitely add value for a true collector. I could be way off, but I'd probably ask $350 minimum for a package that nice.
P.S. I checked eBay and found several similar bikes up for grabs in various states of repair. The prices range from $120-255 for bikes that are not as nice as yours.