Πού να σου εξηγώ τώρα... [GR>EN]

Themis wrote this on p.2 of the discussion of 'an oops moment'. I've come across the idiom πού να σου λέω before but have forgotten what it means; what do this idiom & πού να σου εξηγώ mean? I have a suspicion that they are introductory phrases, which are used to alert the listener to some important news, like the English: "Hey, you know what! Costas has married Marianna!

Πού να σου λέω, πού να σου εξηγώ = Where should I begin talking/explaing...

Σ' ευχαριστώ, αξιότιμε Δρ. Σαφή τώρα είναι όλα.

Αυτό το ξέρω. Έτσι είπε προ πολλού ο Νίκελ σε κάποιο λήμμα. Δεν με νοιάζει καθόλου: πού και πού μου αρέσει έτσι να σε φανταστώ, δρ, χαχαχα.:mellow::twit:

I think more colorful expressions may convey the meaning better:

You won’t get it even if I spend too many words to explain
It would take too long to explain
You don’t really want to know
Oh drop it!

The speaker is trying to dissuade the enquirer from asking.

Thanks, Earion. Come to think of it, the original I once heard was πού να στα λέω. Has that got a different meaning?

No! πού να σ(ου) τα λέω is the equivalent of “Hey, you know what!”, as you wrote in #1. An introductory phrase, used to alert the listener to some important news.

Thanks, Earion! Two definitely distinct meanings, which I shall memorise. So much to learn!