If you’re going to leave the system open for any amount of time, replace the drier/accumulator. When you put 30” of vacuum on the system, it actually boils any moisture out of the lines. Be careful with the amount of oil you put in the compressor. Too much oil will damage the new compressor and cause the expansion valve/orifice tube to malfunction and make noise. There should be a spec as to how much oil you need to add when replacing certain parts in the system.