Testicle displacement after hydrocelectomy - the testicle involved in the hydrocele surgery is stuck at the top of my scrotum. More surgery?

No. If the testicle is located within the scrotom, and outside the abdominal cavity or inguinal canal, you do not another surgery. But make sure the testicle is still well placed and there is no circulation compromise.
No, for your... How long has been after hydrocelectomy? From what stated, i would not recommend to reposition the stuck testis as long as being comfortable and palpable. Such postoperative condition does occur infrequently and usually requires no additional surgery except the one high in inguinal canal in children appearing like an impalpable un-descended testis. Best wish to health, happiness.