6th Gen ('00-'05): MAP sensor
#2
Try Auto Repair and Maintenance Estimates | Auto Shop and Mechanic Ratings to get a ballpark cost. In the mpls/st. paul area the actual cost is usually the higher end of the range. I replaced one on a friends grand am gt and the part was about $45 from O'reilly. Only a couple of screws to remove to replace it so I wouldn't think labor would be much but a shop will probably charge you a lot more for the part.
#4
The map sensor is the black rectangular part the plug wires are going over. It's connector is underneath and you can see the ends of the two screws holding it. Piece of cake to get to.