Ruzzi, always inquire about service history when buying a pre-owned watch; if the seller had the watch serviced, he should, but not always, be able to produce documentation. Although this would most likely be listed in the ad.
Ask the dealer for the serial no. of the XV; the # will give you an approximate date of production and whether the crown is original or replacement. Personally, if the latter, I'd look for another example as this would niggle at me every time I strapped it on. Since you're asking the question, I'd imagine it would bother you too. XV's are pretty rare to find in the 2nd hand market but not impossibly so - be patient and you'll come across another example.
If you don't really care and posted the question because a friend or someone else mentioned the issue, don't ask a thing, buy, wear, be happy, rinse, repeat. Ignorance is bliss.