I'll echo what most others are saying: replace everything you can while you have it off. Over the weekend my 99 E300 started dripping diesel behind the shut off valve. Like yours the intake manifold is coming off so I'm replacing everything. I bought the viton o-rings and hoses from Jim at fryerpower.com (great guy and quick shipping!). For $45 it is worth it to replace everything. Not sure but check to see if the EGR o-ring is included.

What did others do about the fuel lines (the smaller plastic lines w/ the clips)? The o-rings can be replaced w/ viton but what about the hoses themselves? Is there a source for viton or do they matter? I have an indy MB guy doing it on Friday and I want to make sure he has all the parts.