i drive to lahore nearly every month. The first time i went i got lost cause i didnt really know the way but that was around three years ago since then they have really imprved the road and the signage. You can easily find your way. The roads are in pretty good shape in punjab sindh is a little bumpy
i travel in
1990 pajero
costs me around 15000 rs one way
i prefer the pajero because its a bigger car and has no electrical crap that can go wrong and if something does go wrong every bloody mechanic can fix it. As in the past i had taken a prado 2002 and it started giving me a problem , which was the same case as my vigo.
However a city should be good enough for it
Advice would be to try to cross sindh during the day which means leave karachi city around 4 o clock