It's a big job but the only result from low oil pressure is a blown motor so do it ASAP. If you heard grinding then it's possible there are now metal chunks floating around in your oil, if the low pressure doesn't grenade your motor then those will.

There are probably plenty of "while your in there" items to do at the same time. Good luck.

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2002 X5 4.6is - Titanium Silver / Black Alcantara - Dinan Stage 2 - Bilstein/Eibach - Brembo BBK ----SOLD---
1993 318i - Brilliantrot / Tan - bone stock daily driver