I know that this is a long shot and without actually seeing the car it
is difficult to put a price on this car, but I've been offered $6000 and
I'm not sure if I should take it.

The car was originally purchased in 1957 by my great uncle from the
daughter of the Caddy dealer in Tucson.  It was his daily driver in
Tucson until 1994.  It has 72K miles and is all original accept for
having a electric fuel pump added and the power mast replaced with a
rigid mast.  The transmission was rebuilt at 71K. I had it moved to
Massachusetts in 1997.  I've since replaced the master cylinder, all the
belts and hoses, battery and window/door gaskets and kept it tuned up.  
I've also located all the parts for a 1956 power mast.  I have the
original manuals, reprint shop manual as well as the original bill of
sale and cancelled check.

Now for the down side.  There are a few deep scratches on the lower side
of the driver door, there are a few rust spot developing.  The air
conditioning and clock have never worked.  The edge of the driver seat
leather is torn and the cloth inserts are worn.  Paint is original, but
slightly faded.  It was oxidized when I got it, but I was able to wax it
out.  Some of the interior chrome is oxidizing.  The speedometer has
started to act up in cold weather.

A collector asked what I wanted for it and based on previous web
searches I said about $6K.  He answered ok a little too quickly which
leads me to believe I'm under valuing it.  I could use some guidance.  
My last search turned up a guy selling a 56 for 29000 EU, but his has
been completely redone.

And before someone asks, I really don't want to sell it, but I don't
have a place to store it (too long for my garage) and don't have the
time (or cash) for the upkeep.

Thanks in advance for any advise.