Doesn't matter. You can start it up if you are plugged into shore power or not. BUT, if you are starting it up to exercise it (as recommended - once a month), unplug it and turn on the air to put a load on the generator.
Another excellent idea is to change the oil and filter after the first 10 hours.
Added: HWH Kick-Down Leveler; RoadMaster Anti-sway bars; Tornado Rotary Tank Rinser; Accede Backup Sensor Kit; cylinder locks (w/one combo lock); custom sink cover; Kenwood DDX 5706S front radio; Pioneer MVH-X5560BT rear radio; Oxygenics Shower head; ScanGuage II; Blue Ox Tow Bar w/RVi Brake 2; Winegard Rayzar Automatic TV antenna; Trimark Steel door lock; Dometic 310 toilet; whatever is next.