Need to change to a a/c retro fit do i need to change dryer or filter if so how and where is it'' on 10 90 chev z71

Yes change the accumulator /filter drier and the orifice tube the orifice tube is on the high side line going to the condenser and the accumulator is on the fire wall passenger side but this system needs to be evacuated before this is done its against the law to release these gasses into the air so youll need a recovery system to do this dontforget to replace the seals also

No extreme measures need to be performed. They have a small kit that has the new low side quick disconnect adapter for $8 to place on the low side port of the old system. Remove the old schradder valve out very carefully as there could still be high pressure in the system, of the old port prior to installing the new adapter. The new cans of refrigerant require a new adapter for the cans and cost about $3 or you can purchase the bigger cans which come equiped with adapter, hose and ready to go. Get one with leak sealer to condition and help seal the system.