marketpress issues

hi.
1) i have a custom shopping cart in the header.php where i use mp_items_count_in_cart() to display number of items in cart. when clicking add to cart this does not update. it updates only after page refresh. i really need some help getting this to work with ajax or something.
2) is there anyway to display the subtotal outside the cart?
3) im very dissapointed by the lack of documentation of marketpress. is there even any kind of documentation? all i could find where basic videos.

please, save my day and try answearing me on all the above questions.
thanks.
/andreas