I need to replace a Wood Duck house. Can you give me a little more information?
You sound like a responsible landlord. The most important thing to consider when deciding whether or not to put up a Wood Duck nest box, is maintenance. That includes cleaning out the box annually in the fall, adding new wood chips in the spring and replacing boxes as needed. Wood ducks often return to the same nests year after year.
The Wood Duck Aix sponsa is a survivor. Hunted nearly to extinction during early 20th century, careful management procedures and nest box placements have succeeded in raising the population to well over a million. 
Unlike other ducks, the Wood Duck nests in trees. They make their homes out of old Pileated Woodpecker nests and trees that have natural hollows. So it would seem natural, to mount nest boxes on trees, but in order to protect them from predators like raccoons it’s best to mount them on baffled poles. The females or hens readily accept these set-ups, and studies have shown they actually prefer low-mounted boxes.
The best time to put Wood Duck boxes up is now until the beginning of March. The peak nesting period is mid-March to mid-May in Michigan. Boxes put up later will be ready for the next season.
The recommended nest boxes, like the ones found at Wild Birds Unlimited, should be made of high quality wood, have a duckling ladder, an easy side clean out, ventilation, drainage, and cedar shavings for nesting material. Wood Ducks don’t bring any nesting material to the boxes other than a layer of down feathers the mother pulls from her breast and belly.
The best place for a nest is near a wooded area and close to a wetland with lots of bugs. Both the egg-laying hen and her ducklings eat lots of aquatic insects. Box entrances near water should either face the water or away from prevailing winds.
Nest boxes placed on land should be located from 30 to 150 feet away from the shoreline. Make sure the area between the nest box and the water's edge is free of obstacles such as roads or fencing since the hen must lead her ducklings to water soon after they hatch.
It is generally recommended that nest boxes should be placed at least 600 feet apart and should not be visible to one another. Always remember when placing nest boxes, to consider ease of access for monitoring purposes. 
The male and female will probably both visit the nest regularly for two weeks. The female will lay an egg every day until there are about 15 eggs. Then it’s left to the female alone to incubate them for about a month. They all hatch at the same time and 24 hours later leap from the nest with their mother’s encouragement and journey to the water.
The video below shows their jumping day.
1. U.S. Department of the Interior/U.S. Geological Survey http://www.npwrc.usgs.gov/resource/birds/woodduck/wdnbox.htm