How do I replace a bathtub drain trip lever?
Admittedly, I haven't done it before but I came across instructions awhile ago (courtesy of eHow and Google).  Maybe they'll be helpful.

http://www.videojug.com/film/how-to-fix-a-broken-tub-trip-lever

http://www.ehow.com/how_3391064_replace-triplever-bathtub-drain.html

-M