Generally, any template doesn't have such a file:
templates/YOURTEMPLATE/html/com_virtuemart/productdetails/default.phpYou have to create it.
This should work for J1.7+VM2.0.0, but the chnages in the
templates/YOURTEMPLATE/html/com_virtuemart/productdetails/default.php may differ a little. You need basic PHP skill to apply the described changes to a slitly another file.
Basically, you must apply appropriate change to
templates/YOURTEMPLATE/html/com_virtuemart/productdetails/default.php which must be a copy of YOUR
components/com_virtuemart/views/productdetails/tmpl/default.php, not to use the attached. The attached files is for another VM version and is just incompatible.
The second question
http://forum.virtuemart.net/index.php?topic=97365.new;topicseen#new is not clear to me.