I've experienced all my cracks showing through so if I was to do it again in the future, adn I was determined that I would never go back to wood trim (removing vinyl wrap) I'd definitely sand the cracks down with some 1000 or 2000 grit sand papers and then wash them. you'll be happy you did.
see my pics of my vinyl wrap.
http://www.xoutpost.com/944841-post8.html notice in the first picture how my cracks show through my drivers door trim piece?

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I swear, my cars are like a girlfriend.
Sometimes its a rough ride, sometimes its smooth motorin'.
Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
BUT at the end of the day, she loves it when I am inside her.

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'91 850i
'05 X5 4.4i
'09 Clubman S