Hi

Firstly your alternator does have a freewheel type pulley or clutch people call it different things. The pulley works in one direction kinda like the chain sprocket on the rear of a bicycle and yes they do pack up. Mine did and i got it renewed pulley is about £40 or so you need a special tool to remove it. First link below will explain everything.

To replace the alternator :

Put car up on ramps at the front
Remove front accoustic shield 8mm socket 8no.
Remove middle section accoustic shield 8mm socket 4no.
Undo nut from tensioner 13mm
Take weight of tensioner with ext bar and withdraw the bolt to undo tension on belt.
From underneath remove alloy pipe that runs from turbo to intercooler (2 jubilee clips & 2no 10mm bolts)
Disconnect Battery (Becareful with radio code)
Pull off sleeve on heavy wire to back of alternator
Undo heavy wire 13mm
Undo light wire 11mm
There are 2 bolts holding alternator to engine i used hexagonal socket to fit the splined head on these bolts (cant remember size)
Withdraw bolts and remove alternator via the underside of car.

Reverse sequence for installation.

NB Charge pipe needs removed to get alternator off car.

Good Luck

McCool300TD

Few Links for you

http://www.peachparts.com/shopforum/showthread.php?t=164552

http://forums.mercedesclub.org.uk/showthread.php?t=23702

http://www.mbclub.co.uk/forums/showthread.php?t=28134

__________________
1988 190E Sold
1996 C230K Sport Sold
His: 98 E300TD Estate, 7 seater, Avantgarde, Silver, Black cloth, parameter steering, dipping rvm, folding mirrors, rain sensing wipers, pentagon tints, 17" Elegance wheels. 298K
Hers: 93 300TD, 7 seater, Grey MB Tex pearl blue metallic, 15" 8 hole alloys, OTG, Cruise, not much else 220K