I have done this twice on a 601. Used an impact wrench with a 27 mm to take off the main bolt (and to put it back on). Then, you can take out some of the allen bolts so as to take off part of the front pulley. Finally, you can use a puller to remove it. It is not very hard. You do not need any special tools. The only problem is that on a 603 there may not be enough room for the impact wrench. on the 601 190's there is tons of room up front.

An impact wrench can tighten it enough without the locking tool. I did this in 1994 and then again in 2004. About 200kmi inbetween.

__________________
Jovan

'84 (11/83) 190D 2.2 5-Speed; Silver/Blue; Motor No. 00354, 402k mi (340+kmi mine)

'89 Porsche 911 Turbo Coupe; Black/Black; 53kmi
'05 BMW 530i 6-Speed; 302kmi
'19 Range Rover; 30kmi