Hello,
To get data from row you can use getRowData method.
http://www.trirand.com/jqgridwiki/doku.php?id=wiki:methods
You can initilaize the data in the form using the events described here:
http://www.trirand.com/jqgridwiki/doku.php?id=wiki:form_editing#editgridrow
Best Regards
Tony