Reboot Powerconnect 6248 Without Disrupting Configuration

I apologize in advance for the newbie post, and if this is answered elsewhere please point me in the right direction:

I have inherited charge over a LAG/VLAN-based network with a central 2-stack Dell Powerconnect 6248 operating as a core switch and routing traffic between the VLANs that are trunked up to it.

I would like to reboot this switch without losing any configuration as I am just getting into this network I do not want to disrupt or rebuild the configuration.

I can get Telnet or SSH access to the switch but right now am using the GUI. When I go to reboot I choose to reboot both stacks, and am met with the message:

"The device will restart with the start-up configuration, not the running configuration. Would you like to continue?"

I had a separate network contractor reboot the switch previously and I am not sure if he simply ignored the message and proceeded. I would like to be able to reboot this switch without losing any configuration.

My question is, am I ok to proceed through this error message? Or do I need to backup configuration in order to reboot? What is the best way to proceed with a simple reboot of both stacks while retaining the current configuration.