Swap out for 214 Wheels Question

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I have an 07 CPO with 19 inch Sport wheels and brand new tires that I want to sell and get the 20 inch 214 Y Spoke Wheels. I am confused as to what I need to buy to make this a painless process. Can I just by 10x20 front and 11x20 rear and be done? Do I need to buy spacers? If so, what size and or what do the spacers do, I believe they make the wheels stand out wider from the wheel well, but are they necessary, serve a purpose? Do I have to get the fender flares, or is that just for appearance purposes, and finally, what size tires go with the 10x20 and 11x20 set up. Thanks in advance.