Rehearsing for a webinar is always a good idea, especially if you are new to webinar.net.
webinar.net allows you to copy your webinar to use for practice. When you copy the webinar you get everything from your "real" webinar, but it's not associated with your registrants and it serves as a test run.
Follow the instructions in Can I copy a webinar? to copy your webinar.
Practice makes perfect!