Brady whats so hard?, I completed that mission in one time, but anyhow I'm here to help you out
1: do you have an Xbox 360?
1B: do you have an Xbox 360 controller with wire?
1C: do you have vista?
If you have all, put ur Controller into your PC, and go to Driver and go to options and select the controller instead of the keyboard
If you don't have Vista, Put ur usb wire into the PC and let the PC load him, then you should look for "Find drivers on the internet" or something.
Then you should be able to play the game with the Xbox 360 controller so you can easily accomplish the mission.
If you have an other controller specialy for PC? just plug that one in
Hope this helps you out. (It helped me out, looked on the GTA IV cover and they said Xbox 360 controller was compatible, and just tested it out on DPL

)
EDIT: I know you tought I would help you by downloading your save game. But I think you have to do it yourself becuz there are harder missions out there
EDIT2: Ok I'll take your save game

or does any1 already did ?