The window regulator is sold as a complete unit, so if you ordered it you will get the cable and motor. It's pretty easy to change once you know what to do. I haven't change the front door regulator, but I think it is much easier than the back door. To change the window regulator on both the front and back you will need to remove the windows. (just the ones that roll down!)
For the back door, on the inside of the the door, there is a plastic cover that divides the window. Use a screwdriver and push the bottom of that cover to remove it, use care not to scratch it. Underneath the cover, there are 3-4 screws. You will have to remove them. Then , you'll have to roll the window down somehow, or if the window is down far enough, you can remove the screw that bolts the window to the regulator and lower the window. Once you have lowered the window you will need to remove the seal from the divider (black bar). To remove the black bar, tilt it towards the front of the car, pulling up at the same time. This is a little tricky to do, but do it slowly so you won't scratch it. Once the black bar is removed, you will be able to pull the window out. From here it gets much easier. Carefully remove the small clear plastic window on the inside of the door (you will need to put it back). Behind that window is upper bolt that holds the regulator to the door. There is a lower bolt and four screws that bolt the motor to the door. Pull out the window regulator and replace it with the new one.
Although I haven't replace a front window regulator on my 5 series, I have on my 7 series. You will still need to remove the window, but I believe the only thing you will need to do is loosen the bolt that holds it to the regulator. That bolt looks funny, but you can use a standard metric socket on it.
If I get time, I will post a couple of pictures showing the process.