if you have no need for regular blog posts, you can just use those. the post is probably not overly different from a custom post type for a product. though i just did a CPT for products and added some cool features. though since they were related to metaboxes and custom columns there’s no reason you couldn’t add them to posts, but in case you want to use your blog ever, i’d probably keep them as a separate CPT.
the ecommerce plugins i’ve seen are usually related to setting up your shopping cart.
where do you want to import from? you can always import/export your posts w/ the xml built-in import/exporter