Just going by my previous experience with my GT.
My passenger window had stopped working, then a coupe of months later the drivers. Although I could live without the passenger one working, I couldn't not have a working drivers windows.
Anyway, to cut a long storey short, after getting a dealer to rip me off and do nothing but suggest 2x new windows regularots & mechs at ~£300 each, and charge me £100 to tell me this.
I took it upon myself to dismantal the drivers door and have a look myself.
When pressing the switch, I could hear a click, which sounding like it was engageing, but no other noise.
Power was going to the motor when the switch was pressed but, no output from motor.
I disembled the motor, and removed the brushes. Having seen nothing wrong I put it back together, strangley it then worked.
So on passenger side, I just tweaked the brushes slightly with a screwdriver and they popped further in. That motor then worked too.
So in my case it would appear the brushes on the motor were out of possition.
Not had any issues since (2 and a half years later).
As a side note, I also discovered to cause of another common GT problem with passenger door, doing the old stepping and needing to have soft reset (ye olde switch down for 10 seconds then back up for 10 seconds)
The white connetor that goes onto the control unit was a little black around one of the pin holes. upon closer inspection, I could see the plastic was a little melted too. Making me think the connection wasn't good and maybe it had been arcing. So I closed up the gap that the pin goes into and cleaned up the soot.
Again, another old niggle I've had no issues with since doing the above.