This is a '95 e300

Okay, so I've been pretty busy lately but temps are rising so I need to get this fixed. I received the ac temp switch from Fastlane, but when I went to replace it brown fluid started spraying out! I guess I had it wrong, I though it was the pressure switch that would lose refrigerant if taken off. Can anyone shed any light on this? I don't have the tools to check pressures, so I opted to get the part first. Should I give up trying to fix it myself and just go to an ac shop?

Thanks!

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