Done the trip a couple of times takes between 2.5-3 hrs depending on your speed and traffic, but a smooth trip.
leave at 6 and your are parked up at 9, hire your gear (approx €25 a day) buy a ski pass i think €40) and you are on the mountain top at 10. leave at 5 and you are home at 9 latest. When you go on weekday or at least avoid holiday season the ques are not worth mentioning.
Facilities are great, only when you are a fanatic you will be disappointed with the challenge of the slopes, but for the average skier, great fun.
Directions - you can't miss it it is clearly signposted when you approach Granada - just follow the signs Sierra Nevada.
Beware that when it is snowing you might need snow chains, and it is not unusual that they turn back cars without them on the access road....