Everytime you upgrade vBulletin, your hacks will be whiped out. for more help on upgrading vBulletin try looking here
Now, that we have that down, go ahead and reapply file changes according to the vBa products readme file.
Once that is done upload (if nessary) the vBa prodcuts installer to the admincp directory and point your browser at it (eg: mysite.com/forum/admincp/vbacmps_install.php) and select the link that says
"Click here to install ONLY the templates (useful after upgrading vBulletin) -->"
Now if everything went as should you should be running at full speed again