You might as well not replace the tank screen, unless you believe that there are large gobs of the stuff which will block the fuel line.
I have a couple of holes in my tank screen (screwdriver) and I have not needed to replace the pre-filter before the fuel pump in 12 months, I monitor the fuel filter at each service and the fuel pressure while driving.
But, then again, I do not have an infestation of microbes eating my fuel and crapping in my tank.

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.