Umbercode on "Custom CMS ecommerce to wordpress"

I won't say it is impossible, but it will be some work. There is a lot of content on that site which, regardless of how the data will be collated, will be tedious to work through.
First of all it will depend on how you want to setup Wordpress to deal with this data. Once you have a plan for how the new site must be structured, you could probably write a script that translates the old database to the new wordpress database. But even so, you probably need a lot of handwork to check each page and item afterwards and add things like photo's manually.