The BMW wiper arm removal tool is shown in the pic #1 below. It looks like the one in pic #2 but made of steel and is quite heavy.
Note that the body shop may use a different type of tool but works the same way (pics 2 and 3). If you buy the tool from the local auto parts store, make sure it fits the wiper arm bolt as the bolt is bulky.
Let me find the pic from the TIS where it shows the distance from the wiper arm to the top edge of the cowl panel.

BTW, you're right on track. You just need the tool to remove the arms.

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