update usps

I need to update my usps shipping to V4 but cannot, at this time, update my opencart version (1.4., because of all the customization.
Is it possible to search for every instance of usps.php in my existing implementation and replace with files from the updated version of opencart?

Thanks,
Devin

bump

fixed it.

How did you fix this? I'm having problem with USPS myself. I keep getting this error when trying to do a test checkout:

PHP Notice: Error: Unknown column 'unit' in 'where clause'<br />Error No: 1054<br />SELECT DISTINCT weight_class_id FROM weight_class WHERE unit = 'lb' in /home3/johncpit/public_html/johnpittman/opencartnew/system/database/mysql.php on line 49

And I don't know WHY I'm getting this error...

I am getting the exact same error. Running 1.5.2.1 . Any ideas on how to fix this??
thanks,
ritaylo3