kolkata to nepal

i stay at kolkata, want to visit nepal in next year, please guide me
1) how to go there prefer to go by road,
2)what is the suitable time(for the weather basically)to visit Nepal
3)what are the must visits,
4)also inquisitive to know the shopping articles over there for personal usage as well as gifting purpose,
thanks in advance

You can go to Raxual/Birgang and cross over and then take a bus to Kathmandu. You can also go by siliguri kakarvitta but in my view this will be longer.

thanks a lot sujoy and sorry for the delay, can you tell me something in detail about mode of transports and their costs,
thanks once again
anonya