Will the change url affect links

Hi All,
I have just began migrating from single wp site to MU.
On the page network of wordpress sites its recomended for me to change URL site to non www and to proceed with the multisite instalation.. Im not sure if this is going to brake all my previous posts and all other links that I already have on previous single instal(posts,images, …) Im going to use as subdomain instal.
Thank you.