Render/encode the complete audio track out of FCP. You will end up with an ac3 file about 170MiB in size (rough guess). This is small enough to upload at somewhere like sendspace as a single file.
Creating a new disc with the replaced audio is a fairly straightforward process accomplished using a few free Windows tools (PGCDemux, MuxMan and VobBlanker). I mentioned adywan in jest above; he has previously written some step-by-step instructions for doing this which I can dig out.