Yes, you can do all World Heritage Sites tour in Nepal on your own. However, doing it through a travel company and hiring a professional tour guide will be very fruitful for you since you can have the comprehensive assist from him/her including the authentic information about the heritage sites, arrangements of foods and accommodation during the tour and to cope with other minor and major problems that occur during the visit. If you have studies and researched a lot about Nepal and the location of World Heritage Sites, you are confident that you can get them easily and can arrange everything that you required on your own, yes, you go for independent World Heritage Tour in Nepal. But, again, we suggest to take at least a guide for your tour.