In which case Sprogget, to answer your nephew's question fully -
He is now one step further to owning a full legal copy of MSFSX than those who download the trial version and benefits from having some printed material that is not available to downloaders. The trial version is no different in code to his ie it only requires an activation code to give him unfettered access to the program. He may either purchase another copy from Amazon, Play, Ebay etc or pay MS for the code, I do not recommend MS as other routes are cheaper. There is no other legal way.
Nor is there a risk free illegal way, despite being a law abiding type person I keep my ear to the ground and I know of no crack to unlock it, anything that promises to do so is fool's gold, would probably come from a warez type site that carries more viruses than a stinking corpse.
Having looked at a south american net retailer I note that the 'Gold' edition is available for £16.39, hardly a rip off. How much would he like to pay for a trashed hard disk?
Hope this helps. Good luck to him and hope it whets his appetite.