Around here we mostly use blades, not electrics. So it is just possible that no one here knows how to change that trimmer blade. I encourage you to hang around here, but you might get a better answer to this specific question elsewhere. A quick google search tells me that http://www.electricshaverforums.com and http://shavermeister.yuku.com are probably the most active forums for electric shavers.
I agree with the above post. Most of the time here on B&B we are a friendly welcoming group. Of course since most of us use DEs, we are all, for the most part, electric illiterate. I think I can speak for us all when I say that we all deeply apologize for not being able to help you with this question. In the mean time though, we would be happy to convert you to the DE side. We have pinaud (Just a little joke).