Object in a session


I am working on a e-store. I have a page where user puts his
address and info, and also chooses form of shipment. When he/she submits
i want to display the data he/she just entered + add the costs of
shippment. The cart is already in a session and i just add the costs of
shipment to cart total. The question is how should i do this. Is putting
the @order object in a session is the right thing to do, and then after
confirm just save it? Or maybe i am missing something.