In the early stages, Gretna had keeper Greg Fleming to thank for keeping the game level as he did well to keep out long-range efforts from Ross McCormack and Steven McGarry.
Gretna almost opened the scoring themselves in the 20th minute when a long-range effort broke kindly for Fabian Yantorno but the Uruguayan was thwarted by Graeme Smith.
The visitors had three narrow escapes in the 37th minute. Firstly David Clarkson was denied twice by keeper Fleming and defender Gavin Skelton from close range.
A second corner came in and Chris Porter was unlucky to see his header crash back off the inside of the post.
Then a third corner saw Skelton on hand once again to clear a Stephen Craigan header off the line.
The opening goal finally arrived in the 44th minute when Jim Paterson's cross from the left was nodded down by Porter, leaving Clarkson to turn and fire past Fleming from six yards out.
The young Well fans did not have long to wait in the second half for a second goal.
It was scored in the 61st minute when McCormack bent a deep corner to the far post where Craigan rose to head the ball back into the six-yard box for Porter to nod home his seventh of the season.
Gretna did fashion a couple of chances of their own, but Evan Horwood could only fire into the side-netting and Yantorno's free-kick was confidently held by Smith.
The game was put beyond Gretna in the 74th minute when Clarkson added a third. McCormack turned on the edge of the box and laid the ball back to the young striker whose sweet shot found the back of the net via the inside of the post.