The damage suggests that the bike hit something hard like a parked car or large curb, etc. The down tube (and often the top tube) will pucker just behind the head tube lugs, on the bottom side of the tubes. The wheelbase of your bike is now likely just a little short of specification.
The panto crank, if in decent shape, is probably worth $300 or more on the bike you are looking at. If equipped with 1st generation Super Record, the rear derailleur may be worth another $200+ if nice. Any other nice parts will probably put sum of the parts over $500, excluding the frameset.
If the frame rides well, you have two choices. You can either keep it as a rider or have the bent tube(s) replaced and completely re-paint the frame. Luckily, vintage Colnago decals are readily available. Cost of tube replacement, repaint and decals will get you over the $500 mark pretty quickly. This is about what a good Super frame will bring on the bay. Even though it still rides well, the damage will likely make the frame worth next to nothing to a collector.
Jeff Pyzyk
Milwaukee, WI