If you are near an Apple Store I would go there and get the right answers, because they have the part numbers and can tell you exactly what is swappable.
Now, is your 667 the DVI model, or the VGA model?
The 500 and the 667 DVI have different screen resolutions, and therefore different screens, and that might present a problem with swapping parts. If your 667 is the VGA model then you might be in luck.
The burning smell could mean the logic board has fried. That will not be cheap to replace. Probably not worth it in my opinion.
Trust me, taking apart a Titanium display is not for the faint of heart.