Congratulations to you!
Be sure to keep it simple or you may never get going. (Like 90% of people that are fiddling with complicated options)

Webinars on Air is highly inexpensive and the experience for your guests is better than most of the higher priced ones.(WebinarJam would be the other recommendation)

Create simple slides to teach a great bit of value. Pitch your offer clearly after 40 minutes or so of pure value.

Run a test Webinar alone - to get used to controls.
Get this out of the way. The first one will not be amazing so just do it ;)

Sign up for a free trial of GetResponse for your email marketing needs. (I favor this platform for robust features and major simplicity)

You can create an opt in page with Get Response (free for a month) to collect emails of attendees or you can go to leadpages.net and create an opt in.

I'd run ads on Facebook or possibly LinkedIn depending on your offer/target market to get attendees to show up.

Of course there are more tips and tricks to cover but the main idea here is to: get it done and get it out there. From there you will improve.

Use Camtasia for videos, no need for this. It will be recorded through the Webinars on air anyway.

Have fun and go execute!