If you are taking out the old one there is another factor you may want to consider. If you want to run biodiesel in your Benz and haven't completely cleaned out any risidual dino gunk in the tank this will become a problem as the gunk from the residual dino will clog up that in tank screen sediment filter and leave you dead on the side of the road.
The work around would be to strip the screen out completely and install an outside-the-tank filter, either in-line or can type near the outlet port. This would be a lot simpler to change on the side of the road than the screen inside the tank.
Now if biodiesel isn't something you are interested in at all then inside the tank is just fine.
http://oem.overnightautoparts.com/parts/overnightautoparts/wizard.jsp?year=1981&make=MB&model=240-D-002&category=All&part=Fuel+Screen has them.