Your friend is on the right track. All of that should have been done with a compressor changeout. The lines should have all been disconnected, flushed and blown out with dry shop air. Also flush and blow out the evaporator and condenser. Backflush the condenser if it looks dirty. The orfice tube which is in the little line with a flare nut should also have been replaced. If you are using R134a then all O-rings should be replaced with new ones and then add 4ozs ESTER 150 oil to compressor and 2 ozs to a new accumulator(that silver can) and 2 ozs to the condenser. Evacuate the system with a vacuum pump (you have to do this and you can rent one) Then WEIGH in the charge of 32 ozs R134a. You are done. I just converted my 87 over to R134a just like this and i have no complaints. I too live in Hot, Hotter, and My tires just melted! I am a refrigeration tech, and I can tell you if you don't do it right the first time, you will pay to fix it the 2nd time and the 3rd time etc..etc..
E-mail me with pressures and temps. at 1000RPM'* for 2 minutes with Fan on High, and Max with windows and doors closed. Thermometer should be in center vent.