In terms of game compatibility, there is no problem at all, Japanese games will run on a USA PSP without a hitch...
However, not all JP games have an english language setting, for example, my personal favorites Densha De Go! and Jet De Go! are 100% in Japanese, no language settings at all! So I guess it'll be good to find out first, you could try sending the eBay seller a question asking about the language settings?
Cheers,
Fox
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