You have to get permits. Interagency permit station is big building off 395 a few miles south of Lone Pine at turn off to Death Valley. Info re its location is elsewhere on this website.
Your question re navigation gives me concern. Navigating in the snow, particularly above Outlook Camp or Mirror Lake, will not be straightforward at some point. While a GPS is helpful, it is an electronic tool that can fail and should not be relied upon (iPhones are great with GPS-enabled maps installed, but same problem, and you burn through the battery way too quickly ...probably would run out of charge after less than one day if GPS left on continuously). Need to be able to read topo, use a compass. Trail will be covered in snow at some point, very easy to get disoriented unless you have experience with snow travel, use of appropriate tools.
