Don't forget how much it costs to pay someone else to reskin your app!
You could buy some stock graphics or have some made, buy this course and be "in" way less than you would be to may another developer or company to do it for you.
You will also gain valuable knowledge on how to the process works so if you get a quote down the road for another project you will know if it's accurate. Opening up the Xcode project back in October of 2012 for the first app I had created to see how it worked was a great move! That allowed me to "reskin" that app to create my 2nd, 3rd and so on before people ever used the word, "reskinning".