The Irish face the Faroe Islands, Slovakia and host Cyprus with the eight group winners and seven runners-up with the best record against the teams first and third in their section advance to the finals to join the hosts Croatia.
O'Brien insists his side will be taking nothing for granted as they head to the Mediterranean island next week.
"All the countries at this stage of the competition see a massive prize in front of them, which is trying to qualify for the finals," said O'Brien.
"We'll have to be focused in everything we do on the training pitch and in the games. We are happy with our preparation. We got through the first phase, had assessments and training games before Christmas then two friendly games in Spain last month.
"Certain things we did well in those games and in others we can improve upon. We've got players who can score goals but our defence kept clean sheets in the last two games which is a good sign.
"At the start of the season we aimed to have a competitive squad and it has stood to us. Three games in six days is very demanding on young players so its unlikely we'll have the same 11 on the pitch every game. We could be playing in 22-24 degrees too which is something we'll have our work done for. Cyprus will have the advantage being the home side obviously."
O'Brien is adamant that Ireland will take nothing for granted heading into the tournament.
"Some people might look at a group like this and dismiss certain opponents but in youth football any country could develop a crop of players at a certain age group and it may mean nothing in regards to their senior rankings," he added.
"Everything is geared towards game one while we'll have work done on the other opponents. We'll want a good start but the reality is that we can't underestimate any of our opponents."
REPUBLIC OF IRELAND U17 SQUAD:
Brian Maher (St Patrick's Athletic)
Kian Clarke (Bohemians)
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)
Brandon Kavanagh (Bohemians)
Rowan Roache (Blackpool)
Richie O’Farrell (St Patrick's Athletic)
Adam Idah (Corinthians Boys )
Luke Nolan (St Patrick's Athletic)
Gavin Kilkenny (Bournemouth)
Aaron Connolly (Brighton)
Daryl Walsh (Waterford)
Glen McAuley (Liverpool)
Callum Thompson (Wolves)
FIXTURES
UEFA U17 Championships Elite Qualifying Round Group 8
Wednesday, March 15
Republic of Ireland v Faroe Islands, Paphiakos Stadium, Paphos (CYP) (12.15pm Irish)
Friday March 17
Republic of Ireland v Slovakia, Paphiakos Stadium, Paphos (CYP) (12.15pm Irish)
Monday, March 20
Cyprus v Republic of Ireland, Kouklia Community Stadium, Paphos (CYP) (12.00pm Irish)