That's a real common error, which I don't really think is an error, just a warning that the help documents and other stuff installed with the last extention from webassist is being installed again with the extention just say yes to replace. I do all the time and have never had a glich. read above in the notices on install and javascript errors for more info.
And I know Jason put a list of best order to install extentions, I'm just not sure where. Just have a look around a bit and I'm sure you'll find it.