Hi Mark,
The only serious problem I can think of that you may run in to is if the dishwasher water shut-off valve under the sink is broken and won't close. Other than that, it's a pretty simple and straightforward repair.
Here is a rundown (use these diagrams for reference or if you need any parts for this model:
Model GSD1920C07BB):
1. Unplug the power to the dishwasher
2. Turn off the water to the dishwasher
3. Remove the bottom kickplate
4. Remove the two wires from the valve solenoid
5. Remove the inlet water line (1. you'll need some teflon tape to put it back on. 2. Replace the old one if looks bad with one of these
stainless steel hoses)
6. Remove the thin rubber feed tube from the other end of the valve
7. Remove the screws that hold the valve bracket to the dishwasher frame
8. Now do everything in reverse, don't put the kickpanel back on just yet though. Turn the dishwasher on and make sure there are no water leaks.
9. Put the kickpanel on and grab your drink of choice, cause you're done!
Let us know how it goes...