I show 5.5 to 6 hours to replace the oil pump. The genuine BMW oil pump is exceptionally expensive. The other BMW parts I looked at were also really expensive. I would certainly see if there is any independent BMW repair shop in your area that specialize and have knowledge of the M3. Ask them if they have previously replaced the timing chain on one of these BMWs. The timing chain replacement is a very labor intensive job my labor guide shows 30 hours. I hope it is wrong.