Andy Spivey's West Pier side edged out an Edgehill side who were forced to play with 10 men for 60 minutes after Kurtis Henderson's first half dismissal.
It was Edgehill who drew first blood after Kieran Link's tame free-kick was palmed up and into the net by Pier gloveman Scott Wardman.
Pier had shouts for a penalty turned down by referee Jimmy Sutherland, but only two minutes later Kurtis Henderson handled Neil Thomas' strike and Martin Cooper duly slotted in from the spot.
Henderson was shown a yellow card in the process.
A few minutes after Pier's equaliser, Jamie Bradshaw broke at pace and was brought down by Kurtis Henderson, giving Sutherland no choice but to issue a second yellow and subsequent red.
Scores remained locked at 1-1 until the 82nd minute, with the game heading for extra-time a corner was only half cleared by Edgehill and the ball fell to Neil Thomas, who struck through the crowded box and past Callum Myers to win the game for Pier.
Pier boss Spivey singled out midfielder Sam Garnett and wide man Tommy Barker as his side's star men.
Lloyd Henderson was Edgehill's star man.
Newlands await Pier in the final, which will be played on Wednesday April 12 at Pickering Town, despite a lacklustre display against Itis Itis Rovers.
Geoff Nock's side took the lead when Ricky Nock played the ball over the Rovers defence and Drew McCoubrey raced clear to finish.
Scores were level at the break though, Rovers player-manager Mikey Barker chipping the Newlands keeper to make it 1-1.
Newlands regained the lead after 70 minutes, Dan Freer reacting quickest when a shot on goal was blocked to fire Park in front.
The win and Newlands' place in the final was secured when a ball was only cleared as far as midfielder Jack Hakings on the edge of the box, who slammed a superb volley into the top corner.
Freer was Newlands' star man, while Barker singled out right-back Glenn O'Neil as his side's man of the match.