Rep.  Sander Levin of Michigan was chosen this morning as acting chairman of the tax-writing Hous e Ways and Means Committee, a post that plays a major role in health care and billions of dollars in expiring tax cuts.  L e v i n r e p l a c e s C h a r l e s R a n g e l , D-N.Y., who s t e p p e d a s i d e Wednesday as chairman wh i l e t h e House ethics commi t tee investigates his fundraisi n g a n d finances.  Rep.  Fortney "Pete" Stark, D-Calif., held the acting chairmanship for a day under House rules, but Speaker Nancy Pelosi told a meeting of all House Democrats today that Levin was the choice to run the committee.  He will serve until Rangel's ethics case is resolved or a new Congress convenes next year.  Stark will remain chairman of the Ways and Means health subcommittee.  Levin told reporters: "I think you know my close relationship with Charlie.  At this point, I'm acting chairman."