Welcome to the Q&A Forum

One sitewide link probably isn't going to hurt you too much. On the other hand it's probably not going to help you too much either. It is worth pointing out that removing the no-follow from the banner would be a violation of Google's T&Cs regarding paying for links to manipulate Page Rank.

Thanks for even more valuable input I guess i need to run the tool and then see how i can get some good "dofollow" links to back my frontpage up. Am i correct if it could take quite some time for google to catch up on the external links?