The eggs will be fine as long as they don't actually freeze. And, as mentioned above, you can check that by candling (use a bright flashlight in a very dark room--search the forums for "candling" to get pics and more details). Ducks usually lay their eggs in the early morning hours, so the earlier you can collect the eggs, the better chance they will not freeze.
As for incubators, if you've never done it before I recommend you start with an inexpensive but decent quality foam incubator, or one of the nicer plastic sort, that hatch between 10 and 50 eggs. For foam incubators, I like the Hovabator because it is affordable (under $200 with the turner--less than that if you can find one used), effective, widely available, and lets you hatch up to 42 eggs (and trust me, it is an addiction--you will want to hatch more than a few eventually). For plastic, the Brinseas get really good reviews. They are extremely reliable, easy to use, and easy to clean plus durable, but they will also cost more--a 20-egg
Brinsea costs a little more than the 42-egg Hovabator. So it comes down to priorities.
Once you're addicted, you may find you need something like a Sportsman or Dickey (cabinet incubators that can hold hundreds of eggs), but unless you find an exceptional deal (like the $300 one--I would jump on that if I could find a deal like it), it's a pretty enormous investment for something you may or may not get excited about.
Okay, who am I kidding? You WILL get excited about it. But practicalities being what they are, you may never need the extra capacity of a large incubator and by the time you do, the cost will seem unimportant.