Do I need to take my bmw 645 to the dealer to replace the battery.

call your dealer or any bmw dealer

You will need a good OBD2 scan tool.
try this you tube link

apart from a diagnostic test which before pulling out any more money would get thsi done it could be a few things faulty plugs coils or worst case ecu which is where the spark gets sent from or regulated from but get it checked first as it should show up on the test what it is

you need to replace the wear sensor it will rest itself

Take it to the BMW car dealer. He can make one or order one. Take your title or some proof you own the car to show him. On some cars the key is programes to work on the car's computer. Have him ck to see why the car is acting that way.

Yes you can do it your self.

is there anything extra i need to know on changing the battery on my 2005 645ci bmw

LMAO take it back to the dealer and tell him to reset the ECM since he was stupid enough to onhook the battery and not reset it!

sounds like the control module or a micro switch has become defective. You need a dealer diagnostic really.

how do i reset my computer after a sterring malfuntion light came on