Thanks for updating Quest. i have a quick library module and demo (with walkthrough) for anyone interested.
To use:
1. Have a Boolean attribute on your shop called "shop" set to true.
2. Have an integer attrubute on the player called "money", set to the
amount of cash the player starts with. It would be good to set this
as a status attribute too.
3. Any goods for sale should be placed in the shop. Set to scenery and
not takeable (these will be changed when the item is purchased).
They also need an integer attribute "price"; this will be deducted
from the player's money.