Where the site was built in 2008, It was Most Likely eCart 3 that was used to create the shopping cart.
It would be best to manually update the FedEx files for the time being, then recreate the shopping cart down the road using eCart 5.
the eCart 3 shopping cart is not easilly updated using eCart 5.
the fed ex files can be downloaded here:
http://www.webassist.com/webassist/actions/do_download.php?file=109/330/WA_eCart_FedEx_PHP.zip&from=/community/tutorials/view_tutorial.php