From his description it sounds like he's talking about the 210 chassis. The manifold does not have to come off to replace the fuel lines, but the coolant reservoir does. My personal opinion is that you have much better access with the manifold off. Once you've removed the manifold a few times, that becomes about a ten minute job and is well worth it to me. There is a metal gasket needed for the manifold. An excellent description of the job was done several years ago by Lightman - a search should being it up. The air bubble in the fuel line by the prefilter is not something to be concerned about. If you haven't replaced your fuel lines in a very long time, then that is certainly good insurance. Also anytime you disturb the prefilter, you must change that O ring.

You should also make sure you aren't leaking on top of the injector pump from the delivery valves. That area should be bone dry. If there is any wetness there, new O rings are needed. Lots of info on the delivery valves on the forum too.

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles