A/C questions

Ok...a/c has not worked properly in 3 years but I never have cared...now that someone doesn't want her hair messed up, I am exploring what may be wrong. Heeding the warnings and advice of some who have posted here, I had a refer fitter friend slap his gauges on it (yes they were 134a). At an ambient temp (measured from a couple inches in front of the condensor) of

70, we had 66 on the probe stuck in the center vent. The pressures on the evaporator side ranged from a low of 45psi to a high of 65psi whereupon the compressor kicked off then on again when it reached the low reading. The high discharge side ranged from 50psi to 65psi...yes...those were the correct readings...We both thought that before we went further and tried evacuated and charged it, that I should check here....The FSM shows that with a higher evaporator pressure and a low compressor discharge there are two possibilities; defective compressor or low charge. Should we add refrigerant, evacuate and add refrigerant, or replace the compressor? Ideas sure are appreciated and encouraged.