As for how to identify the start point, I would recommend simply ripping the GOUT AC3 file to disc. Place it in the first audio track in Womble. Then load in your preservation mix in the second audio track. Play, and nudge it left or right one frame at a time (trimming the starting frames if necessary) until it comes into sync. Mute the original and export the modified preservation mix to WAV. It will add/strip the frames in the export process and otherwise leave the audio untouched.
Unfortunately, Womble is only accurate to the frame, and not to the millisecond like Vegas. But will anybody notice? As long as it is accurate to the frame, it's pretty much unnoticible to anybody.
The most accurate way to sync would be with a multi-track audio tool like Vegas. The drawback here is that you would have to convert the GOUT AC3 to WAV first (unless there is a plugin/newer version that lets you place a stereo AC3 file directly into Vegas as a track). Such a conversion could hose the accuracy of the reference file.
I'd recommend the Womble approach (those guys need to start paying me for promoting their product so much).