Hi,
1. this is not documented yet, although it might not be what you are looking for, the Autocomplete API is basically JavaScript file which allows to convert field in to autocomplete input but, the AJAX function which will return autocomplete values you would need to write yourself.
Either way by the end of the week when i will have some free time i should be able to post an example how to use it and i will update this thread.
2. i am not sure to be honest, this seems like a great feature to have, but it also might be theme dependent, i would need to investigate it.