I am replacing the Refrigerant Control Valve in the A/C Compressor of my 1999 Buick Regal. I was getting high pressure levels on the low side and found the posting on the faulty RCV. I have a new accumulator and before I start to put everything back together I need to replace the orifice tube. Do I need to undo the two lines that go into the firewall? The orifice tube was the cheapest of all the replacement parts but it is causing me the biggest headache. Please help.