just bought polo 1.4 tdi

hey all. i just bought a vw polo 1.4 se pd tdi 5dr hatchback (mk4?)

i know there are some problems with it and wondering are they big problems and how much would you gues to fix?

Nearside Rear Brake disc(s) slightly pitted (3.5.1h)

Offside Rear Brake disc(s) slightly pitted (3.5.1h)

All brake discs heavely corroded

those were from the last MOT test and I'm gonna get them fixed but are they expensive jobs?

another 2 things. the drivers side electric window switchs dont work. the passengers does. would that be a big job?

and when i start the car it makes a noise like when you try to change a gear without the clutch and you hear that grinding noise. :s other than a;l that its cool :)

Thanks for any help.