bangkok - kolkata - kathmandu - lhasa - beijing

hi
iam planing a trip from bangkok - kolkata - kathmandu - lhasa - beijing.

I plan to fly to kolkata from bangkok and get the train to raxaul which is on the border of nepal. its from here i can not et enough info.
does anyone know what the bus are like from raxual(india) to kathmandu, is it daly/weekly etc,
also i heard that there is a bus from kathmandu to Lhasa very tuesdays and fridays for about $70, Is this true. or would it be better to fly?

what is like to trek the base camp in april? will i need to book or can i get a tour when iget to kathmandu?

Finaly is it true that there is a a new railway line from Lhasa to Beijing? has anyone travelled this line? is it open to tourists and how do i get a visa for china/tibet if crossing by land...

any kind of help/opinion would be great
cheers

Hi,
You should get a toursits permit if you want to travell to Lhasa.
Have a nice trip!

is it possible to travell from Kathmandu to Lhasa by flight and then travel to beijing by train from Lhasa? can i get a visa at the air port in Lhasa?