Well, who agreed to share their home with the SPL new-boys following their promotion to the top-flight at the end of last season, delighted the unfamiliar 'travelling' faithful with a victory which further consolidated their place in the top half of the fledgling table.
Motherwell manager Mark McGhee handed striker Ross McCormack his first start of the campaign in place of Chris Porter, who was dropped the bench.
And the visitors made the best possible start after taking the lead in the eighth minute.
A Jim Paterson cross landed nicely for Keith Lasley at the back edge of the 18-yard box and the midfielder's cross-cum-shot somehow looped over keeper Greg Fleming and inside the far post.
Ten minutes later the home side were level as the Motherwell defence failed to deal with a Craig Barr long throw and the full-back's return cross back into the box was headed home by the unmarked Abdul Osman from ten yards.
Gretna came closest again before the break when Gavin Skelton latched on to a Colin McMenamin cross-field pass, but the full back was unlucky to see his left-foot shot dip over Graeme Smith but crash off the bar and bounce clear.
The second half burst into life after twelve minutes when Barr tripped David Clarkson and was show his second yellow card of the afternoon.
In the protest following the decision, Gretna boss Davie Irons was sent to the stands.
Five minutes later Well took the lead as McCormack fashioned space for himself 30 yards out and sent a shot goalwards and, thanks to a neat deflection from Porter, the ball nestled in the bottom right-hand corner of the net.
As often happens it was the side with a man less who looked the more likely with David Graham having two shots blocked by Motherwell defenders.
But Well held on for their third win of the season despite struggling against the ten men for most of the second half.