You can change the oil pressure switch from the top.
Remove the 2 screws from the coolant tank and move it over toward the radiator. ( don't forget to unplug the sensor on the bottom of the tank)
This give you clearance to reach the switch. I believe the deep socket is 24mm. When reinstalling put some paper towel in the socket to help with installation. Other wise the switch will be pushed into the socket when trying to reinstall.
Use a BMW switch, it is about $20 bucks at the dealer. ( It centers the o-ring on the switch to prevent leaks). I installed a $8 aftermarket one and it leaked. Hope this helps!
11 Audi A5 2.0T 8 Spd Tripotronic w Sport Pkg, 19" Anthracite Wheels
12 VW CC 2.0T [/B] stock
05 VW GTI 1.8 T 5 Spd, Coilovers, Big Brakes,
04 BMW 645 CiC Auto
97 VW Jetta Jazz 5 SPD
06 Mazda 6 Grand Sport Auto
05 BMW X5 3.0 6 SPD
05 Infiniti G35 6 SPD
04 Volvo S60 "R" 6 SPD
99 Nissan Maxima 5 SPD
91 Nissan 300ZX 5 SPD
92 Honda Prelude Si Auto
76 Fiat Spyder 124 5 SPD