SOLUTION FOR MULTIPLE GALLERIES
Using the code from @WTCOC, you can hack the autoplay to work on multiple galleries by duplicating the whole code and replacing one line:
In the duplicated code, change:
You should be able to do this as many times necessary for the number of galleries on your page by repeating the code and changing the number. It may not be the most concise approach but it get's the job done with little effort, especially if you're not comfortable modifying the body of the code!