2 Modifications

My site is Modernlanguages.org, I’m trying to achieve 2 things;

1: When a user logs in, the ‘register/login’ button on the navbar changes to a different label/link (‘My Profile’). Also the ‘purchase’ button on the navbar shouldn’t be visible to level 1 subscribers.

2: On http://www.modernlanguages.org/wp-login.php?action=register , I want to change the ‘Register for this site’ text

I have very little experience with WordPress, but I am competent with most semi-technical terms (heavy experience with vBulletin plugins/modifications) so any help is greatly appreciated.