Hello gazfun,
This modd is different than the present version of the PeninsularWar Modd.
With the new version, and JMM's developments, our modd for the Waterloo Campaign will add new nations and new units for our scenarios. But existing nations and units in the standard game are not affected by the installation of the modd. So with this modd installed, you will be able to play all other scenarios of the original game, as if nothing had happened...
The modd also enhances the sounds of the game. So on this aspect only, it is likely to have an impact on the original game.
I hope I have answered your questions.
Regards,
EricJ