Please see pages 34-38 in this document about converting simple workbooks (e.g. no VBA):
On this:
"Is there any complexity in converting 3.5 bex workbooks to analysis, do i really 1st convert 3.5 workbooks to 7.x books then converting them to analyis workbooks.. ? In this process do i really convert 3.5 quires to 7.x quires.."
Looks like Bharath Ramamurthy already replied to you here:
SAP BusinessObjects Analysis Office 1.3 – BEx Workbook Conversion Details + Q&A