I changed the driver side inner door handle. I did it myself.
Thanks to stevelaw and Dexterous for providing valuable information.
I purchased the part from the toyota dealer for $30 (including tax). Here is the part description.
Description: DOOR HANDLE LH
Part No: 69206-02050-E0
Make: Toyota Genuine Parts
The process will be little different depending upon what part broke off from your old door handle. But the door handle that you purchase from the dealer is complete part. You don't need to use anything from your old door handle. So in the process of removing the old door handle if something brakes, do not worry.
Please note that you DO NOT need to remove door panel to put the inner door handle.
First remove the old door handle. There is a small screw in the center of the door handle cup. Remove the screw and slowly slide the door handle cup forward (towards the front). With the help of the flat panel screw driver, loosen the cup from all the side and slowly pull it out. I broke one edge of the old door handle while doing this. But again as I said before, do not worry. You do not need anything from the old plastic door handle. You will see a hole once the old door handle is completely out.
There is a metal rod with a bent tip in the hole where the door handle ‘cup’ was mounted. Just reach inside and grab the metal rod. You have to put that metal rod with bent tip inside the hole of the new door handle. In addition the new door handle has a white moving clip that needs to be attached to the metal rod. Just align the white moving clip and push forward towards the metal rod till it latches on to the metal rod. The white clip keeps the rod tip from sliding out or becoming loose.
After that, the door handle ‘cup’ piece could be placed back into the door panel, make sure you slide it backward until it lock into the door frame and the screw hole should match-up if done right.