Other parts needed when changing A/C compressor?

Hi,

When I change the A/C Compressor, what else does it need to be replaced ? Is that necessary to replace the A/C Schrader Valve, Expansion Valve and A/C Pressure switch too ? I’ve heard about the A/C Receiver Drier also, but I am not familiar with these parts. Can somebody help me to decide what exactly do I need ?
Mileage: 74000, 2001 SAAB 9.5 2.3t.

Thank you,
Laszlo

Multiple sources say that the drier needs to be replaced when the A/C system is opened...it is likened to changing the oil filter when you change the oil. I've also read that the expansion valve needs to be done, but the main thing I keep hearing is to replace the drier.