This one you really, really don’t want.
One of the three cables that operate the driver’s door window on my car broke. Two choices then present themselves: you buy a secondhand mechanism (assuming you don’t want to spend several hundred on a new one) or you buy a repair kit which has new cables and a new pulley. Either way you have to take the outer door skin off (for the repair kit) or the whole lot off (new mechanism). I’m cheap and lazy, I went for the repair kit. I ended up with two repair kits because the pulley on the first one was the mirror image of the existing one. We wound up using it, but that’s another story.
Anyway, after half a day struggling I gave up on it and brought the car to the mechanic almost next door who asked me to take out the entire mechanism and he’d put it up on a table so as to have room to work. That meant drilling out five rivets, another job you don’t want.
It took four of us to put two cables on a pulley with sufficient tension. It’s at about this point we realised why Smart don’t sell a repair kit.
Next, he riveted the mechanism in again so we had this:
Yes, everything had to come off the door. Today everything had to go back on. Door card (two parts, the outer one is a nightmare), door skin (nightmare, especially when you realise it’s almost on and you’ve forgotten to put the glass in), glass (easyish), mirror (fairly easy until you realise that it has to come off again because the window seal has to go under it), window seal (looks easy until you realise that you have to push it much harder to get it to seat properly than you thought).
In summary: if you’re ever asked to help repairing a window winding mechanism on a Smart Roadster, say “no!” firmly and loudly. Come to think of it, you’re probably best advised to say “no!” whatever it is.