I'd buy the filter from TPS to be certain you're getting OEM quality - it won't be an expensive part of the job and you know it'll be right.
For oil - not sure on D3s and what the out of warranty specs are that the Americans recommend? For my D2 the Fuchs Pro Race S is Ester based but not Audi approved.
For later cars Millers Nanodrive seems to be popular
If in doubt stick to the recommended options from the Castrol oil chooser on TPS and it'll still be cheaper than the main dealer and done the way you want it 
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===SOLD===2002 Audi S8 D2 Final Edition (yes, really) in Avus Silver with purple extended leather===SOLD===
2011 S5 Sportback in Phantom Black with black Super Sports leather, 9x20s, tech pack high, adaptive xenon plus, intelligent key, memory seats pack, sunroof, B&O, Audi Drive Select & quattro Sports Diff, DAB, parking system plus
2015 VW Golf GTI Performance Pack in Carbon Grey with black Vienna leather, tech pack (Discovery Pro nav & Dynaudio), DCC, factory towbar and retrofit RVC
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