air conditioning recharge DIY

[emmydotnet]

I am going to replace the expansion valve, drier and pressure switches on my 91 560SEL. Compressor is good so will not replace it. symptom is no cooling and low side goes to vacuum once clutch is engaged. static pressure is good about 85psi. It is an R12 system.

I need a DIY instructions on evacuating and recharging. I will have a shop discharge and recycle the R12 before replacing exp valve. Do I need to add mineral oil to compressor? Your help would be appreciated.