Hi - I see this question was posted some time ago, so you may already have found the solution you need. As someone who regularly does business training webinars, I'm happy to share a few things I've learned along the way.
1. Have at least 2 people in your staff who are trained experts in managing the technical aspects of the webinar. That way, if one is away, sick, etc., you're not scrambling for a back-up. But ideally, 2 staff are overseeing the live webinar process. If something goes wrong, 1 or both should be able to resolve issues quickly.
2. Test the webinar each day for 3 days prior to the webinar date. I've had to reupload PPT presentations several times during the testing days because of issues with my slides. It may sound excessive, but you'll identify issues each time during testing and will be able to address without stress because you have plenty of time to resolve. Also, and this is key, the more issues you can address ahead of time, the better trained your staff become in webinar management.
3. Do a rehearsal of the webinar (partial or full) 1 or 2 days prior. Have some staff or associates attend so they can give feedback on any content or technical issues.
4. Assure your attendees that the webinar will be recorded in case of technical issues. I've attended live webinars with some big business names where there were thousands attending, and was amazed at the technical issues that were happening. You wouldn't expect it at that level but, it's technology, so stuff breaks down, usually at the worst possible time.