This is an easy home-owner repair!
1. Get down on the floor with a flashlight and a 5/16 nut driver, and remove the two screws holding the lower panel. Those screws are located beneath the lower panel, so you'll have your head on the floor to see 'em!
2. Lift the lower panel up and out.
3. Using the nut driver, remove the two kick-plate screws and lay the kick-plate aside.
4. Discard the broken spring.
5, Look at the remaining spring to determine where the spring should hook.
6. Hook the spring at the bottom, then use sturdy long-nose pliers to grasp the upper spring hook and slightly stretch the spring to hook it at the top. With the dishwasher door closed, the spring isn't under much tension, so it's not physically difficult to hook the top of the spring.
7. I bought two springs, and opted to replace the unbroken spring. Assumed that if one broke, the other wasn't far behind.
8. Replace the kick-plate and secure with two screws.
9. Replace the lower panel and secure with two screws. You will have to pull down on the front panel to get the screw holes to align - you be compressing a rubber gasket at the top of the front panel.
10. Test the door operation. With new springs, the door will likely offer a tad more resistance when opening.