I think you’re letting yourself get too worried about this.
The route from McCarran airport is quite simple and stays mostly on major roads.
Here’s Google’s route
https://www.google.co.uk/maps/dir/McCarran+International+Airport,+5757+Wayne+Newton+Blvd,+Las+Vegas,+NV+89119,+United+States/Sheri’s+Ranch+Brothel,+10551+Homestead+Rd,+Pahrump,+NV+89061,+United+States/@36.0688648,-116.1000964,9z/data=!3m1!4b1!4m13!4m12!1m5!1m1!1s0x80c8c59f1f049c5d:0x471359241ec41e1e!2m2!1d-115.153739!2d36.084!1m5!1m1!1s0x80c63e73b7f22383:0x86e6dbef648f16bc!2m2!1d-115.956434!2d36.070751?hl=en
Many of the larger car rental companies will also rent out satellite navigation units for less than $10/day. Alternatively you can buy new or re-furbished units from Wal-Mart for less than $100.
