Delete/Cancel PO lines

We have open PO's that date back several years, we want to close them.  I have a few questions and need some additional information  

1. Is there a way to update and close each PO without manually going into each PO and closing?
2. If there is no way to mass update the PO lines, could we do a world writer for those PO's with a last sts of 380, to change the next sts to 999?  Will this cause any intergrity issues?  By do this, would it update all fields associated with the PO?
3. We have some PO's that are in next sts 440, do these need to be closed by going into each PO and closing or is there another way to update these?