J,

Not necesary to drain fuel tank or clean strainer unless it is plugged and won't pass fuel. If you notice a difference in performance in a full tank verses an almost empty tank, then the in-tank filter is starting to get plugged probably by algea. You will need to put an algeaside in the tank to kill any algae if there is any in the tank. Don't put new filters on because any algae might contaminate them and you will have to replace them again. Leave the original filters in place and if they don't plug, they don't have to be replaced at all.

I know it seems illogical but the inline filter is called thre primary and the canister filter is called the secondary. I guess they were named in the order the fuel flows thru them.

$800 is a very resonable price. I've paid more for parts cars.

I suggest synthetic oil for the engine. Rotella Synthetic , Mobil 1, Delvac 1 or Castrol Syntec are good choices.

Factory repair manuald used to be ordered directly from MB USA. A form was available from dealers. I don't know if this service is still available. Check with a MB dealer. Newer MB have CDs instead of books but I don't know if they are available for the older MB. All are expensive as is anything you buy from MB.

P E H