You can most definitely seek professional help and advise anywhere you are, regardless of the period of time you're there or where you live, and it's entirely possible that a psych could diagnose you based on one visit if that's what it was limited to and all you wanted was an "unofficial" dx and some guidance on learning about who you are personally.
However, if you want an "official" dx for some outside purpose (especially if you want educational accommodations, which require a certain significant amount of documentation) most likely the diagnosing psych will want to meet over several sessions at least, and perhaps perform a number of tests, so it would probably require more than a week's worth of visits.