Here's how I did it:
I went into my local Garda Station, Henry Street in Limerick and asked the lady behind the counter about obtaining a Police Cert for the U.S. Embassy. She gave me the form and told me to fill it out in BLACK pen only. She said the Embassy were really strict about that. I filled it out and she took the form back and said it would take about 1 month and would be posted to address I gave. Bring your passport, cos I think you need to fill in your passport number. I can't remember exactly what was asked. And your name MUST be exactly as it is on your passport.
It's your local Garda Station that should help you with this, and the Embassy will not request it, you have to get it yourself. Go back in and explain why it's needed and that it HAS to be you who requests this cert, not the Embassy. You probably got some-one who hasn't a clue.
Good Luck with the feckers!