Hi Somya, so you have reached Sikkim ????. If you want to travel alone then you can ask your hotel to arranged a North Sikkim tour Package that includes everything from fooding, lodging, sightseeing and the vehicle. No worries at all. The hotel will take care of everything. When me and my boyfriend were in Sikkim our hotel manager was so helpful with the tour package. The tour package starts from 16k for entire North Sikkim. Hope this helps. If you want to know more, you can inbox me.
If you are traveling alone, than private vehicles can get very expensive. You can opt for Shared Sumo instead and explore the places yourself. Ask any local for directions or Homestays. The locals are very friendly.