In all honesty, I've looked around for a little bit after reading your post and I can't nail down an exact value for your brakes or levers because I'm not sure what generation they are (definitely very early though). Rough estimate? I would say the brakeset you have (with levers) has to be valued in the hundreds of dollars (note that's a plural, as in at least 200, but probably more!) I do know that Shimano was the first company to go to a dual pivot brake caliper, and before seeing your brakes I didn't know they had ever mono-pivot DA brakes. So you could be sitting on a gold mine man, though again I'm not sure. I agree that the best thing to do to find out more is like one of the other commenters said above and try to find some model numbers printed on either them or the packaging (usually DA has some sort of 7*00 number to designate generations) the newest one (that isn't electronic) is 7900 just for reference.
The front derailleur I would say anywhere from $30-60 depending on how much you like the person buying it/taking into account it's brand new in a box. If you're having a tough time with research I'll tell you this. If it were mine? I'd take it into a trustworthy bike shop (trustworthy being the operative term here) and see what they think. Usually the older guys in there are familiar with this kind of stuff because they probably raced or wrenched on it at some point back in the day. Just my personal opinion though. Good luck. At the very least it's a cool piece of cycling history!