Hi there, I have had all my scans at Hamilton Radiology (at various branches around the city) and they were all great experiences. A standard 2D scan at 20 weeks will tell you the baby's gender - if it decides to co-operate.
I just had a 3D/4D scan at 29 weeks at Hamilton Radiology's main branch at Anglesea Clinic which was pricey, but absolutely amazing. There is only a small window in which they can perform this scan (about 28-32 weeks) as the amniotic fluid needs to be plentiful to get a good picture.
As for the sonographer, you get whoever is on that day. Good luck!