You'll have a job getting the alternator back on without slackening the belt. Just remember to loosent he big (17mm?) bolt through the middle of the tensioner before touching the adjuster rod. If you do break it they cost peanuts anyway.
'08 Chrysler 300CRD (MB OM 642 engine)
'95 E220 estate
'89 230TE (R.I.P.)