My son has a men's 1985 Panasonic Sport 500. I've never weighed it but 30 lbs seems about right.
The Shimano OEM components work fine, if in an unrefined way. The bike is a fine rider, smooth and stable.

With its Hi-Ten steel frame and fork I wouldn't bother upgrading the OEM components.

Here is a link to a catalog page.

http://picasaweb.google.com/scarsgo/...13146655793202

And here's a pic of his bike.