Hi there,
1) anyone trying to access the old url will get redirected
Yes, your http://gerrypatt.wordpress.com URL will still work just fine, even if you add a custom domain. You can also choose which one you want to be the primary domain under Store > Domains.
http://en.support.wordpress.com/domains/#setting-the-primary-domain
2) the many incoming links I have to the blog will work.
Yes, all your older incoming links will still work.
Just let us know if you have any other questions.