The 'Locals route' is to take 160 to Pahrump and then just north of town take Bell Vista Ave/ State line road to Death valley junction, turn right on 127 and immediate left onto 190. You will see the Armagosa opera house at the junction. Before Furnace Creek you could stop at Zabriske Point and then from Furnace Creek head to Badwater Basin and Artists drive on the way back as it's one way starting from the southern end. The sand dunes are near Stovepipe Wells and could be seen as part of your ongoing journey next day. And yes you have enough time. There are shops and gas stations south of the Strip where I am sure you will find what you want.