Autom.trans, oil line fitting

Now that I've figured the routing of the new oil cooler hoses, I need to know if I need a special tool to disconect the oil line at the radiator.
They have a small plastic ring (locking ring??) leaning against the fitting, I can push that away from the fitting , how can I remove that oil line ? should I unscrew the fitting from the radiator instead ?
man the life was so simple when a fitting was a fitting, when we had point condenser etc...need for me to go back to school, too many years passed by ;-))
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