I need a Go To Meeting tech expert!

Looking for a Go To Meeting expert to assist on a webinar for 1.5 hours in a couple of weeks. My client has set up a webinar which has 100 registrants and they're a bit nervous about having to deal with any technical issues on the day (e.g.: participants not managing to log-in, audio issues etc). You'd need to be available to assist and talk people through any problems they might have so that the webinar can run smoothly. GTM offers this service, but it is very expensive! We need to keep costs down.