I'm fairly new here but I just finished the section of our training about domain names, so this information is fresh in my mind. In the training video, Kyle says that while .com is ideal, .net and .org are fine to use when .com is taken. Of course, you can also use a different domain name for which .com is available. Good luck!

Won't make a difference. Though most people by default think .com, since WA encourages SEO as a strategy, people will be looking based on keyword and won't really pay attention to the extension.

It'll be just fine - these days TLDs don't matter too much when it comes to ranking, it's more just about "word of mouth"... People by default generally just tend to type in a web address with the .com at the end, so whilst a .com is preferable - if you can't get one it's not the end of the world :)