"Hello everyone!" 여러분 안녕하세요! "Merry Christmas everyone!" 여러분 메리크리스예요~

Yes, it's 여러분! (yo-ro-bun) Note that the 'o' sound is not the long 'ohhh' down on the lips, but a perkier 'o' at the back of the mouth, as in 'top', usually written as 'eo' (not a dipthong... how confusing). The 'u' in 분/bun is also a short 'u'.

et 모두들

여러분,여러분들,다들,너희들 (전부),니네들 (전부),