First let me clarify - IFU = Instructions for Use?
Who is relabeling? The new company or the original manufacturer? At a minimum, if the new company is relabeling, they would be required to register - see the link below:
http://www.fda.gov/MedicalDevices/D...urDevice/RegistrationandListing/ucm053165.htm
I suspect they would need a 510(k) as well but perhaps a more experienced Cover could steer you in the right direction.
If the original manufacturer is relabeling and the new label still contains their identify as a manufacturer, then:
a) no 510(k) is needed; the model or brand change can be handled in a letter to file (for example, a labeling design change that updates the DHF and DMR)
b) the new distributer is simply a distributer and does not need to register or submit a 510(k)