My project needs a store which only involves quotable items, that is, no price is assigned to any given item, instead, the customer adds the items to the cart normally and submits the cart summary to the store owner as a 'quotation request'.

(1) Given the current Store module as a base, how easy would it be to modify the module to have a quote cart?

(2) No pricing and and no payment step is needed. Are pricing and payment parts independently separated from the other parts or are they mixed in a dirty way and one needs to separate them?

(3) Which classes should I start the modification with?

(4) Is there any way to only 'overwrite' the module and not modify it so that when a new release is available, I do not have to start the modification over and over.

buendia