The Group D rivals meet at the Veltins Arena in contrasting moods, with Ireland having taken maximum points from their two outings - beating Georgia 2-1 before hammering Gibraltar 7-0 on Saturday.
Germany, meanwhile, suffered their first defeat to Poland in Warsaw on the same day, having previously struggled to a 2-1 win over Scotland in their group opener.
Goals from Arkadiusz Milik and Sebastian Mila condemned Germany to their first defeat in 19 competitive outings and their only loss in qualifying since a reversal against Czech Republic in in 2007.
With Joachim Low's relatively new-look side finding their feet after winning the World Cup in Brazil, O'Neill is confident his players will ask questions of their opponents in Gelsenkirchen.
Ireland shipped nine goals against Germany when the nations were paired in Group C of qualifying for this year's World Cup, and O'Neill warned neither he nor his side will get carried away by their strong start.
"We're not good enough to get carried away but we've won this game [Gibraltar], scored some goals and we could have got one or two more," he said.
"What I really wanted was to go [to Germany] with six points and we are. The players will feel pretty good right now.
"I think if you go there and sit in for the whole night then Germany will find a way in behind you. We have some attacking options and I think it's important that we go there and try to cause them problems."
For Low and Germany, it will be a case of trying to return to winning ways as soon as possible after an out-of-sorts performance in the Polish capital.
A sluggish showing only really improved once Germany went behind and, while debutant Karim Bellarabi impressed for the visitors, Low was left with plenty to ponder.
However, the long-serving Germany coach does not feel the defeat is cause for panic.
"I've had a slight feeling this week that things haven't been coming as naturally to us. Our attitude and our focus was fine but the young players need to gain experience," he told the DFB's official website.
"We've now lost a qualifier again after 33 games unbeaten; that can happen sometimes. We will try and learn from it. I don't see any major problems in our qualifying campaign.
"However, we know that we will have to put everything into it. We've lost this game, but the ball keeps on rolling on Tuesday.
"Ireland's tactics will be similar. They're a side that predominantly defend and play on the counter. We will talk about our finishing and how we can convert chances like we had."
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