Sorry I don't come to this forum often, so I didn't see your post till now, but I do know what to do with gourds.
You need to let it dry, which will take a while, from a couple months up to a year depending on the size & type of gourd & weather conditions. You'll want to keep it in a well-ventilated place, off the ground if possible, or turn it from time to time to allow it to dry evenly. It'll probably dry faster if you scrape off the skin while it's green. Or leave it on. If you leave it on it will get a little mouldy, but that won't affect its usefulness and can be cleaned off later if you want (a copper pot scrubbing pad and water works well).
Once it's dry (it will turn a tan color and be light in weight) you can cut a whole in the gourd and shake out the seeds. Gourds are easy to grow; plant the seeds after your last frost and give them plenty of water and you will have several more fun gourds next year! Be careful of the dust from the dried up interior of the gourd, though. It can irritate the throat. Wear a dust mask and work outside if possible. You can fill the gourd with water and scrape out the inside stuff if you want.
As far as a birdhouse goes, most birds are particular about both the size of the gourd and size of the hole, so you might want to check out a book from the library for help.
Hope this helps. Have fun and let us know how it comes out!