If you call around the rental places you can rent a pump and gauges for under $40.00. It's what I do although as much A/C work I should just buy the pump
I had to replace the expansion valve on the 64 t-bird and man what a royal PIA. It is located under the dash above the steering. Covered with several inches of black tar looking stuff, and has enough space to get one hand up there. I will never complain about how MB built A/C units again. I still have about 40 dash pieces to get back together and many vacuum lines to connect.