Minecraft skins for Windows 10 and Pocket Edition

For the textures, you can easily change it by changing the terrain.png file with your desired texture pack. But beware that PC's terrain.png may vary with PE's. Try searching for a similar or exact texture on the Minecraft Forums. They have lots of ported texture pack.

For maps, you will need to first port it because MCPE maps aren't infinite and a portion of the world will need to be cut, pasted and then saved in MCPE format. Then you can transfer it to your Android device.

Note: My previous answer was for iOS devices. I have changed my answer to fit the question and hope it helps.

This is a quirk that you sometimes get on the App Store. Usually, you can just press buy again, and after you enter your password, it tells you something like:

You have already brought this product and will not be charged again.

However, if you don't want to risk it, you can either: check the "Purchased" tab, anything you download of the Purchased tab should be free, as you own it, or, you could download your purchases onto iTunes, and then sync them on to your device.