Adding language packs

[Guest]

Hi

 

Our store currently only has the default language pack for UK installed. That means for a product the URL is along the lines of

 

http://www.graphskill.co.uk/8437-m6-wing-nut-a4-stainless-steel.html

 

If I add in the French language pack ,then I believe the link will change to include the language so /en and /fr will be introduced

 

What will happen with our current SEO rankings. Will google see that a thousand product links no longer exist and mark us down?

 

Also what will happen if a customer follows a google link, or a book mark to the above Url - will they get the 404 page?