As kramerpup said, number of cross platform issues, fonts are the biggest one. Most other things will work fine.
But you are correct about how to do it, take your PC .dir file onto the mac and make your projector again.
Remember that mac and PCs use different file targeting though, this isn't usually an issue if you have all files in one folder but if you have files in a number of folders you may want to set your searchpaths. Or you can do a check for mac or pc and use code in all your paths to switch the "\" with ":".
eg
if the enviroment.platform = "windows,32" then
pathseparator = "\"
else
pathseparator = ":"
end if
gotomovie pathseparator & "pathname" & pathseparator & file
hope this helps