if you want to goto Skardu and you also want a road trip.
Go till Islamabad, Park your car at the long parking area Islamabad Airport (400 / Day)
Go to Skardu by air from islamabad. Use a local tour guide with a Prado road around like a local, What locals can show you, You can never experience on self drive.
Karachi to Skardu one way is atleast 4 nights by cars.
Day 1 Faisalabad or Multan (12 to 15 hours depending on how far or fast you go / Non Stop)
Day2 Islamabad (atleast 7 to 8 hours)
Day 3 Naran or Batakundi Atleast (7 to 9 hours of drive)
Day 4 If you are lucky babusar doesnt close you can go reach Skardu in 12 hours minimum.
Similar route at return.
PS : Even if you reach Skardu by your car their are alot of sight seeing places where your car cannot go, You would still need to hire a 4x4 vehicle and still need parking space to park your car if you go anywhere over night.