I have downloaded the new mamewah and I have one question......How do i replace the existing mamewah with the fewist headaches? I have multiple emulators configured with screenshots ect, and I would prefer not to start over. Can I just replace the executable?
You can just replace the executable....
...but your old CFG files will not work

You could print out the contents of your old CFG files, and then add the details into your newly generated CFG files. Alternatively, you could wait for a new version of David Butlers 'MAMEWAH Setup', which should be able to convert the CFG files for you.
At some point I must have a go at making the CFG files backward compatible...