After the break Nacewa and Warriors replacement fly-half Duncan Weir traded two penalties apiece but Leinster failed to capitalise on their concerted pressure whereas the visitors were clinical with their chance - Peter Horne dashing over to seal an historic win.
It was a first win of the RaboDirect Pro12 season for Glasgow - and Campbell believes it was only a matter of time before the Warriors showed their true colours.
"Leinster are one of the top teams in Europe and they're the Heineken Cup champions and I don't think they've been beaten here for two years before now," said Campbell.
"But I think in the last 20 minutes the defence from us was exceptional.
"They put a lot of pressure on us and we didn't buckle. What we've been doing in the last few weeks has really come to fruition.
"We really came back in the second half and upped our game. We really put our game onto them and compounded it at the end.
"Everything you dream of as a child is to come to a place like this in front of 11,000. And winning really is the stuff dreams are made of.
"There is no real greater challenge in Europe bar a few places to come and win so it proves we can step up and deliver."
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