GI wrote:
I tried to install a programmable thermostat over the weekend. It is a
one thermostat household with an air & gas furnace set-up (the wires to
the thermostat were W, R, G, Y--I think).

I took the old mercury thermostat off. When I tried to place the new
wires on, after a couple of bad insulation strip jobs, a wire or was to
short to connect. Since this was attached to the heating unit, I
thought I could at least turn it on and get AC until I can get a
professional out to fix the job. When I switched the breakers, nothing
happened. So I tried to put on the old thermostat, but now of a couple
of the wires are too short.

My Question:
Can the professional solder or extend the copper wires to make them
long enough to attach a new thermostat? I ran this by a HVAC tech that
comes well recommended, and he thought he might have to run new wires
from the HVAC units to the thermostat--is this necessary, or can these
wires just be extended from their existing location?

You should be able to extend the wires, one way or another. At worst,
you might have to enlarge the hole a bit for access and patch it
afterwards.