While pulling up FCC info for this question: Can anyone locate specs on this wifi module? I noticed that the module was listed as modular, valid for any printer that had one of two voltage regulators (The regulator was part of the printer, not on the wifi module).
Even more, when searching for this, found two things. The first is a Hermon Labs Powerpoint/PDF guide to FCC Certification, which includes a section on what does and does not require changes. And the second is the controlling FCC rule on permissible changes without recertification, CFR (2010) Title 47 (Vol 1) Section 2-1043(a)
§2.1043 Changes in certificated equipment.
(a) Except as provided in paragraph (b)(3) of this section, changes to the basic frequency determining and stabilizing circuitry (including clock or data rates), frequency multiplication stages, basic modulator circuit or maximum power or field strength ratings shall not be performed without application for and authorization of a new grant of certification. Variations in electrical or mechanical construction, other than these indicated items, are permitted provided the variations either do not affect the characteristics required to be reported to the Commission or the variations are made in compliance with the other provisions of this section. Changes to the software installed in a transmitter that do not affect the radio frequency emissions do not require a filing with the Commission and may be made by parties other than the holder of the grant of certification.
Furthermore, the FCC Permissive Change Policy 2(c) explains the test behind what is an equivalent chip for the Transmitter Portion, for Class 2 changes:
(i) The new chip component is pin-for-pin compatible.
(ii) The new chip has the same basic function as the old chip, from an external perspective (internal circuitry may differ).
(iii) No change in radio parameters has occurred.
(iv) The same conditions apply when a small area (approximately the same area as the chip) of the PCB is replaced with an equivalent chip.
Based on this, a change to a different version of the same chip family, without any other changes to the board, especially a part that's not related to the intentional radiating parts, would not require recertification nor notifying the FCC. It should plainly fall under a Class I Permissive Change.
Class I permissive change includes those modifications which do not degrade the characteristics reported (2.1043(b-1)).
But, the main thing, you could have both tested under the same FCC ID in the first place. If you are worried about it, that is the best thing to do.