I am giving my old Nissan 89' p/u to my son for his first vehicle. The problem is the a/c quit working on it about a year ago. I noticed that the compressor had apparently been leaking (oily residue behind the clutch). I bought a new compressor dryer and expansion valve. I have put them all on and replaced the o-ring seals at all the connections. The question is do I need to blow out all the lines and evaporator prior to having the system recharged? I also got the conversion kit from r12 to r134a. The other question is does it have to have compressor oil added or is the amount in the r134a adiquate? thanks for any help.