Hi, and welcome to Moz! Here are some of the resources we have that can help, and some answers to your questions.
Our help hub is at http://moz.com/help, and the getting started guide at http://moz.com/help/guides/getting-started is a great place to start.
We offer a series of onboarding emails to help with your site. In the first couple of days after you sign up for Pro, you should receive a message with several tips for improving your site with Moz Analytics.
Here's some background about why we don't have a help desk phone number anymore: http://moz.com/help/guides/moz-procedures/phone-support. As a side note, I've been in the help desk area when we did take phone calls, and there would often be phone calls that would last half an hour while we determined that what the caller was looking for was an SEO services company, and we wouldn't be able to help them, but it took considerable time away from valid help desk tickets.
For billing and account questions, we do have live chat available from that section of your profile.
We do know it's complex, and we're trying to help out new users by adding more getting started information. Thanks so much for your feedback!