Second O-ring on a triple source probe - how to replace?

Does anyone have any experience in replacing the second O-ring in a
triple source socket? I am not talking about the third small O-ring
but the second O-ring which is the same as the first. Taking it out
was not difficult but putting a new one in might be a different story.
I thought there might be someone out there who has done it and who is
willing to give me some hints.