J Williamson , Dec 13, 2009; 10:37 a.m.
Can't speak to the OP's question about buying gear but I was there some years back and during a walking tour around the Ben Thanh Market I came upon a little side street full of antique shops and the like... anyway right smack in the middle of this block of shops was a nice, bright, modern glass fronted place that looked very out of place. You could see inside the whole place from the sidewalk. They were working cameras!!! I looked up and sure enough this was an Authorized Nikon Service Center. What luck... I had two Nikormat FT bodies an older, used F4 that I'd just bought in Hong Kong and 4 non-AI lenses with me.
I had the lot cleaned and serviced overnight for $50usd.
From what I remember the place was on Le Cong Kieu (just east off the round-about near Hen Thanh Market) but Google Maps says the service center is now on Ho Tung Mau about 4 blocks due East from the round-about.