I installed a new Sanden AC pump on my IH 5088 the other day along with a new Hi Press. to condenser line, Expansion valve, and Drier. 

I am wondering how long and how low the vacuum needs to be to get out all the moisture? Will a cheap single stage pump get it low enough to be adequate or is a dual stage be required? 

Do I need to connect the gauge to both the high and Low side or is connecting just to Lo side OK to vac it down?