Settling my 8 week old son in his crib instead of rocking?

i have a hard time getting my baby to sleep a bit more through the night.he sleeps beautifuly during the day,and falls asleep at 8 nearly every night,but he wakes up 2-3 times a night and usually stays awake from 3.30 till about 7.im exhausted.a girlfriend to day told me a technique her midwife told her to do so i can just put him in his crib with him falling asleep on his own and having a better sleep without me rocking him for an hr.it involves wropping them,put down in crib,letting them winge and cry hysterically for over 5 min then going in and rocking the cradle.i tried it today and my heart broke and i started bawling my eyes out.at the end after 8 min,i picked him up and he fell asleep in my arms and he has been asleep for 2 hrs,(its day time here in sydney)do u think its ok to do this?he is 8 weeks old,and my friends daughter is 5 weeks and now only waking up once during the night,she didnt even go to the toilet b4 she started doing this.what do u think?any other ideas for me ?