What the HP support person is trying to get you to do is to setup a real home router to support your network. That way when your Jetpack is power cycled or leaves the network your Netgear will remain online and an continue to support your home devices.
When you disable the DHCP service on the Jetpack we assume the Netgear has one of its own and will take over those responsibilities automatically. You can only have one DHCP service on a network at a time otherwise there could be IP Address conflicts. Disabling DHCP on the Jetpack should force it to behave more like a traditional modem only device where all it does is provide gateway functionality to the internet and nothing more.
Should you do it? That depends on how well its working right now. Perhaps your Netgear already has this functionality built into it and will be fine. It all depends on your comfort level for configuring the home network and the performance of the Jetpack. Generally speaking its always better to be in control of something like this and designate one device to run the DHCP for your network. Any changes you make in this area will be a one time change, unless you need to reset the Jetpack which is often a common troubleshooting step.
Since you are going through the trouble to disable DHCP another good tip would also be to limit the number of connections to the Jetpack by enforcing a MAC filter. With MAC filters your Jetpack will only allow the Netgear to connect to it. This forces any future devices to connect the way you want them to while in your home.
Once you have MAC filtering enabled you could go one step further and configure a higher entropy WiFi password on the Jetpack. The default passwords on a Jetpack can be brute force attacked and cracked within hours. It is always a good idea to create your own custom WiFi password that uses security best practices to secure it from malicious users. Beefing up the security on your Jetpack should be manageable because from this point on all devices should be connecting through your Netgear instead, although I'd advise you do the same on that device too.
Strong password best practices:
http://windows.microsoft.com/en-us/windows-vista/tips-for-creating-a-strong-password
How secure is your password:
https://howsecureismypassword.net/
(Rule of thumb is the longer the better, shoot for atleast a few years to crack)
Lots of info here, hope it is useful to you. let us know if you have any other questions.