D'Arcy's 30th-minute score contributed to an 11-6 half-time lead for the Pool 2 winners, with Fitzgerald crossing early in the second period and O'Driscoll finishing the rout with just over an hour played.
A total of 82,208 supporters witnessed a thrilling encounter as Leinster dominated the majority of the match despite playing for 65 minutes without starting fly-half Felipe Contepomi.
A Contepomi drop goal from the edge of the Munster 22 edged Leinster in front after a quarter of an hour but Munster hit back with three points of their own just a minute later.
Ronan O'Gara's 40-metre penalty levelled the scores as Leinster found themselves unnecessarily down to 14-men after a moment of indiscretion from young prop Cian Healey. The 21-year-old body checked Ian Dowling as the Munster wing chased his own chip ahead and was immediately given 10 minutes in the sin bin by referee Nigel Owens.
A Rocky Elsom break almost resulted in a Leinster try with 25 minutes gone but the Australian flanker was brought down just 10 metres short. Leinster did at least gain a further three points courtesy of a straight-forward penalty but they lost Contepomi to injury in the same passage of play.
The Argentinean playmaker, who departs for Toulon at the end of the season, limped from the field to be replaced by Jonathan Sexton, whose first task was to kick his side 6-3 in front from 25 metres out and 12 metres to the left of the uprights.
The first try of the match came courtesy of a searing break from Leinster full back Ica Nacewa. When Sexton found O'Driscoll with a long, flat pass following a lineout on halfway, Nacewa timed his run perfectly to slice straight through in midfield. The Fijian international took play up to the opposition 22 before supplying a scoring pass to D'Arcy. The 2005 British & Irish Lion was brought down by Keith Earls just short of the tryline but his momentum carried him over to move Leinster 11-3 in front.
Sexton missed the difficult conversion before Munster had the last say of the first period thanks to a second O'Gara penalty, but it was Leinster who claimed the crucial score just three minutes after the interval.
Again the try came through a flowing backline move with two long cut out passes eventually creating the space for Fitzgerald to cross wide on the left. Quick hands from Shane Horgan gave Fitzgerald a glimpse of the line and the 21-year-old finished superbly, stepping inside before bursting through a weak tackle from Paul Warwick.
Sexton added a well-struck conversion from just inside the five-metre line as Leinster established a 12 point lead from which Munster never looked like coming back.
O'Driscoll then put the game beyond the reigning European champions with a 60-metre interception to send the blue sections of Croke Park went absolutely wild.
Munster attempted to force their way back into the match and dominated the majority of the remaining 20 minutes but, just as it had been in their quarter-final victory over Harlequins, Leinster's scramble defence ensured it is they who will travel to Murrayfield for the Heineken Cup Final on Saturday, May 23.