To use the Signs, type on the second line of a sign. You should get a message saying "elevatorsign created but not linked". Then, above it (on the next floor of your shop), in the same space (same x and z values) type on the second line of another sign. Your chat should say "elevatorsign created and linked" in green letters. That means you did it right. If not, then check if you did exactly as I said. (Its kind of hard to explain, but the Wiki has a better tutorial here:
http://mc.minetown.net/wiki/index.php/Lift_Sign) The shop plugin we use now is called Duckshop. To use it, type the information like so (without brackets)
<Your Name>
<What you're selling>
<What Customer is paying>
<leave empty>
So, you should get something like this:
VVAnonymousVV
64 stone
1 goldingot
<invalid>
Then, load your products into a chest, (remember to /cprivate it!) and type /duckshop link.
Punch the sign, then the chest, and you should get a message saying something like "sign successfully linked". Punch your sign again and it should look something like this:
VVAnonymousVV
64 stone
1 goldingot
+++++++++
For clarification, you can always refer to the wiki! Here's the link:
http://mc.minetown.net/wiki/index.php/Duckshop When somebody buys one of your items, the gold will automatically be deposited into the chest. Also, the chest does not have to be under the sign! It can be anywhere in the world (or any of the worlds, although I wouldn't put it in the nether if I were you)
Hope this helps!