Yes, 120mm on the rear and 80mm on the side, the side fan will draw cool air in and the rear fan will suck out the warm air.
depends on his heat sink. if its the standard intel/amd flat heatsink with a fan on top I would skip the side fan.
it its a tower heatsink I would go with an exhaust fan to help pull heat off.
frankly i find side panel fans useless, as do many people