I’m afraid you can’t use the particle FCC/IC certificate (ie modular certification) in a product with more than one radio - and yes, the PN532 is a radio; you may not have been able to use modular cert based on your custom antenna too. You will need to re-do testing from scratch. See section V of https://apps.fcc.gov/eas/comments/GetPublishedDocument.html?id=50&tn=916170
Depending on where you are based, NWEMC are good - I’ve been to both their Irvine, CA and Portland, OR labs. FCC/IC testing, last time we had a quote, was $4k for testing, plus $2k in documentation fees and $4k for the FCC and IC applications (2k each) - that was just for the 15c testing, you’ll need your 15b testing too, and with multiple radios it will get more expensive.
I would strongly recommend that you do ESD testing too, which isn’t required for FCC (but is for CE). Shipping with no idea about your ESD resilience can be expensive, because you don’t know if your device will survive the kind of static discharges that are common in some very dry parts of the US.
One other thing to note is that when the wifi module is in test mode (driven by a PC running broadcom’s WL.EXE application) you will need to work out how to drive your PN532, as the module won’t be doing anything else. You may need to use a bis pirate or similar to get the PN532 in a transmitting mode, as they will want to test both wifi and NFC running concurrently.