A/C Could be the aux fan not working.
I just had the AC service port seals done and complete evac/recharge for around $160.
Do a search for the stalling issue. I remember reading others had it.
I also had the tranny fluid changed for much less than you were quoted.
A good indy service location will save you $$$

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2021 X5 xDrive40i
2015 X5 xDrive35i MSport
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