Try to keep it short, it's a title that will be also used in a menu. Free translation. The page will be about the languages where there are not enough experts.
हमें विशेषजà¥à¤ž चाहिये = We need an expert. हमें विशेषजों की ज़रूरत है! would be the appropriate one with the punctuation mark included.
The singular & pleural for the word विशेषजà¥à¤ž is THE same. Thus the sentence is valid for both "We need expert" & "We need experts" The other suggested sentence is valid, too.
well...I dunno. My dictionary lists only विशेषजà¥à¤žà¥‹à¤‚ as plural of विशेषजà¥à¤ž. Its a small dictionary. And online dictionaries for Hindi aren't that extensive.