How much will it cost to replace the two front driver door hinges? They are beginning to sag...

Unfortunately I don't have the price for replacing the hinges, usually is the body shop that performs that type of work. All the hinges have some play, you may just need to adjust the door lock striker.

Which piece is this?

The striker is the part on the body. Here is an image,

Thanks! Where does one order the hinges from???? How much about?