Have fun getting to the orifice tube

Have some new O-rings handy since you're opening everything up and may need to replace some. Should be the green O-rings IIRC.

Make sure you use the correct type and amount of PAG oil. Once you get it drawn down to the 29Hg mark close it off and keep the gauges on it. It shouldn't drop if the system is sealed. Once you have a good sealed and vac'd system I'd take it to a shop and have it refilled.