Right outside the main gate (Craig Rd/Nellis Blvd, near Las Vegas Blvd) is a WalMart...plenty of parking available for a tractor-trailer, and their policy allows it for several days. Across the street (Craig Rd) to the north of the WalMart are a couple of motels to stay in if you need it.
Otherwise, go northeast on LV Blvd from the GL facility (you will enter/exit from Range Rd, at the light at LV Blvd make a LEFT to go northeast) to Hollywood Blvd, which is about 1.5 miles up LV Blvd, and make another LEFT onto Hollywood. Follow this for about a mile until you come to the Petro/Valero truckstop. There is plenty of parking, showers are available inside the truck stop, and the food is good there (I work right next to it).
OR, you could park it at the truck stop at Craig Rd/I-15 behind the Shell station (northwest corner of Craig/Pecos).
Be sure to secure everything as best you can; the area that has grown up around Nellis isn't the best and stuff disappears all too quickly around there if it isn't secured/locked up.
HTH.
