Can't help feeling that Boston missed their best chance of progressing in the first game against 10 men. Boston have lost all but one of their games at Skelmersdale - the only win coming in 1974. But I still have faith so I'm going for:
Skelmersdale United 0-1 Boston United (161)
As it's a cup game with the possibility of extra time and penalties, as usual in these cases predictions are for the score at the end of normal time.