As per the Hertz Gold benefits summary here , if you are regular Hertz Gold then you are not entitled to any upgrade benefits. If you are a Hertz Five Star member then you get one car class upgrade subject to availability, and if you are a President's Club member then it's a confirmed one car class upgrade. There are some small earning bonuses for 5* and PC but it's pretty lackluster. In short, if you are not 5* or PC, there won't really be any benefit at all for you to use Gold vs. non-Gold.

All of that said, you should check with your insurance company to see how the insurance rental process works.. If you can book it online and then have them reimburse you, then you can just login to your Hertz Gold account online and book it yourself. If they need to book it for you, then it shouldn't be a problem to at least have the agent at the rental counter apply your Hertz Gold member number when you arrive to get whatever benefits you are entitled to.