when a primary domain becomes a redirect and the redirect becomes the primary...

This is probably an odd question, but here goes... I have a primary domain name that doesn't match the total content of the site as it has evolved; however I do have a redirected (to the site) domain name that does.
I would like to swap them around, so that the redirected domain becomes the primary, and vice versa.
But I am concerned I will lose fb likes and links displayed via the social widget on each page, as what was the primary domain would then be only a redirect.

Help... it is a bit confusing but I am hoping someone can shed light on this. I don't want to lose my likes, but I don't want to wreck my seo either....

Thanks!
Simone