you will be able to reach till Kaghan on normal vehical but may need a 4x4 to go beyond Kaghan.. it will be damn cold specailly in nights so be ready for it 
hoteling option will also be very limited.. in last January there was only one hotel open in Kaghan and none was in Naran.. any way, it was a superb trip and Naran was like a lonely planet as compare to Summer 