Shipping fix in a plug in on a Magento open source website

I'm looking for assistance with debugging an issue with shipping options not displaying properly on my Magento open source website. I'm comfortable with the existing code, but could use help getting to the root of the problem and fixing it. I'm not sure if there are any specific tools or platforms that need to be integrated into the project, so I'm open to suggestions from experienced developers.
The exact problem is USPS changed the name of "First Class" rate to "Ground Advantage", so now my website only offers "Priority". I'd like it to offer "Ground Advantage", but I believe the shipping is a plug-in, and I can't navigate that myself.