I would like to add some content/module above the cart (OPC from VM UIkit), to inform clients about things like delayed delivery, holiday closings etc. is this possible?
I'd check top and onepage_promo_top module positions
ps: If you go to admin -> system -> site templates -> options (top right) and enable Preview Module Positions, you can check the available module positions using tp=1 url parameter, like
mydomain.com/cart?tp=1 or mydomain.com/index.php?option=com_virtuemart&view=cart&tp=1
