[Psalm_Kuru]

Hey Everyone, I've got a couple questions regarding some maintainence, firstly regards to the oil level sensors I've got currently 130,000K Kms not Miles, and I haven't got history of the oil level sensor being replaced? Previous owner being my grandmother who isn't entirely sure, should I wait till it eventually breaks/says inactive, or replace it? ( Would Aftermarket cause problems? )

Second would be do the Oil Filter Housing Bolts need to be replaced when doing the gasket? I replaced it about 3 months ago but it didn't fully stop leaking its showing signs of leakage even after replacement which is just bugging me, I believe I didn't torque it properly or the seal itself got nipped or something but I am looking to replace that again.

Third regarding the x2 Vanos Solienoid Seals at the front if the engine, is there anything special you've got to do to replace the seals or just pull out, replace, reinstall?

Thanks Everyone.