Re: general question about adding shopping features to a site
however im not sure if this is the best soloution for them. How easy/difficult is it to add shopping cart features to an already existing site?
Zen Cart is not meant to be "parted-out" into an existing site. You can incorporate the look and information from the original site into Zen Cart.
Please do not PM for support issues: a private solution doesn't benefit the community.
Be careful with unsolicited advice via email or PM - Make sure the person you are talking to is a reliable source.