现有网站的Zen cart

Of course ZenCart can be used to build an entire website that is an eCommerce store, but can ZenCart be used on an existing site, sort of as a "module?"

Let's say I currently have a website, and I have decided to sell some products (add eCommerce functionality), but I want to keep the look and feel (CSS and general layout) of the original site. Is ZenCart a good fit for this purpose? I have seen some websites that have a completely different look and feel when the site visitor goes into the eCommerce portion of a site. I don't want that.

My questions:

1. So, can ZenCart be used sort of like a "widget" or a "module", embedded on an existing (php) web page?
2. If yes, is there a tutorial for how this is done?
3. If no, do you have a suggestion for a different "drop-in" cart module?