The Irish team meet the Faroes in the Cypriot coastal city of Paphos (Kick-off is 12.15pm Irish time) looking for a strong start in the mini-tournament.
The Group winners and seven runners-up with the best record against the teams first and third in their section advance to join the hosts Croatia in the finals tournament in May.
"We've finished our final preparations. Everybody is in good spirits, fit to play and looking forward to the game," said O’Brien.
"Throughout the season we’ve been adding on the building blocks for the players. The players have been looking forward to this tournament and know the importance of it. Game 1 is upon us and we’ve got to focus on that and make sure mindset is right.
"The Faroes have a lot of discipline and strength in the middle of the park. They have some talented players but we’ve looked at the footage and there are areas of their play that we need to be aware of and also areas we can hope to exploit.
"Getting a good start is very important in tournament football. Our players are very aware and know it is very important to get a good start but we need to be calm and not be too worked up because we want to make sure we’re still involved on the final day of the tournament as well as being ready for the first game.
"It’s been warm here but the kick-off time is fine. The players saw the pitch and the surface is excellent so there can be no excuses on that front."
Republic of Ireland Under 17 Squad
Goalkeepers: Brian Maher (St Patrick's Athletic), Kian Clarke (Bohemians)
Defenders: Lee O'Connor (Manchester United), Kameron Ledwidge (St Kevin's Boys), Nathan Collins (Cherry Orchard), Jordan Doherty (Sheffield United), Aaron Bolger (Shamrock Rovers), Conor Coventry (West Ham United).
Midfielders: Brandon Kavanagh (Bohemians), Rowan Roche (Blackpool), Richie O'Farrell (St Patrick's Athletic), Gavin Kilkenny (Bournemouth), Daryl Walsh (Waterford), Ronan Manning (Galway United), Luke Nolan (St Patrick's Athletic)
Forwards: Adam Idah (Corinthians Boys), Glen McAuley (Liverpool), Aaron Connolly (Brighton & Hove Albion).
Fixtures
UEFA U17 European Championships Elite Qualifying Round - Group 8
Wednesday, 15 March: Republic of Ireland v Faroe Islands, Paphiakos Stadium, Paphos (CYP), KO 12:15
Friday, 17 March: Republic of Ireland v Slovakia, Paphiakos Stadium, Paphos (CYP), KO 12:15
Monday, 20 March: Republic of Ireland v Cyprus, Kouklia Community Stadium, Paphos (CYP), KO 12:00