1. To get the theme onto your Dingoo, you must have the custom firmware from TeamDingoo (
http://dingoo-digital.com/). The latest version is A320-1.03TD-3. Once you install that onto your Dingoo (there is instruction on how to), then you copy the res folder into system\res folder. This will replace your current Theme with your one. I would, as a personal thing, create a backup of the current res folder on your dingoo, so if you ever want the normal res folder, you have a backup. You can also use it as a template.
2. Currently, there is no true way of fixing the issues with the genesis emulator. Your best bet would be to get Dingux (
www.dingux.com) and get the genesis emulator with that (I'm pretty sure there is one that is stable). Other then that, you could try frameskipping but that probably won't fix your sound.
Good luck!