using an .htaccess file you can redirect your old product pages to your new ones. search engines will pick this up over time, but it will help those people that click on old links, they'll get to the right place.
I'd also suggest creating a friendlier 404 page, so you don't lose visitors.
It looks like you've got an xml sitemap, make sure its updated with the new URLs.
definitely investigate your crawl errors.
hope that helps.
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