Perhaps "circlip" wasn't the best term; it's more of a very thin closed C-shaped wire with some springiness in it. You can't use traditional circlip pliers on it, for example, to compress it. (It's a bit like those plastic parts with one way tabs that snap together one time only during assembly.)
If I were you, I'd proceed by buying the fitting first - Ford part # F5RZ-3R608-B about $ 6-8 bucks - just to be safe. I say this because I think the fitting is intended to be installed once only and removing it will probably destroy or damage the circlip/ C-clip. Could be wrong on that though.
I would also suggest you remove the fitting from the ps line by carefully applied brute force. I didn't have to do that operation - I had a new fitting and new OEM ps line (parts came separately) - so anyone else who with experience on that can chirp in.