Enabling SEO Add-on

My shop has been running for about 18 months using standard URL's (product_id=1234)

I am considering activating the SEO Add-on but many of my product listings have links to other listings within the full description and I have losts of external links to category and product pages as well.

So my question are;

  1. If I activate the SEO Add-on will the original links still work or will they simply hit 404 pages?

  2. If I activate the SEO Add-on can I deactivate and switch back to standard URL's in the future without affecting the site (other than any external SEO links that will not work).

    Anything else i should be aware of before activating the Add-on?

  1. The old links will still work. No worries
  2. This will affect your seo ranking because if the seo addon is disabled, the seo url will not work