Is the master switch in the lock position? After that you would need to start tracing wiring and follow the test procedures for testing the master switch. Perhaps even check for damaged wires where the harness goes from the drivers door to the body. Do the windows work off the switches on the other doors. There is a company that independent auto repair shops buy their information from that the same information inexpensively to do it yourselfers. The information is year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online
I have had a problem on my villager at the drivers door switch assembly the contacts in the switch keep getting corroded. I remove the switch assembly and litely burnish the contacts with 600 grit emery cloth and everything works good for a couple of years and I have to do it again.