Its called a hear liner. You can do it yourself or you can get it done. If you do it yourself go to a local fabric store, find a fabric you like and are comfotable with and purchase a can of 3M (adhesive spray) and then spray the roof and press the head liner on, after that tuck the sides into the cracks of the car with a screwdriver.
If you are going to get it done professionally they are going to charge you for the fabric and for labor.
Its your choice.
Best of Luck.