This is something I threw together when having to relink a couple dozen InfoPath libraries all containing 100-1000 forms. Why Microsoft doesn't have a check all button at the top of the page is beyond me. Here it is...
1) Open the library. Click Settings -> Form Library Settings -> Relink documents to this Library
2) Open this page in SharePoint designer.
2) Add this to the top of the page after the <Form> tag.
<script type="text/javascript" language="javascript">
function CheckAll(chk)
{
for (i = 0; i < chk.length; i++)
chk[i].checked = true ;
}
</script>
<input type="button" value="Check All" onclick="CheckAll(document.aspnetForm.chkRepair)" >
3) Save, Refresh the page, click and thank me :)!