What should I expect/prepare for if my dog becomes pregnant?

I've never had a chow but my experience is that the mumma dog has morning sickness early on, she may just go off her food for a bit or she may actually be sick a few times, later her appetite will increase then toward the end she will have small amounts more frequently and be very lethargic as her belly swells
She should make herself a nest for birthing as the time approches and should give birth without too much difficulty or assistance required. Depending on your dogs temperament she may like attention at this time or may prefer her privacy, just keep an eye on her without too much interference if you see a puppy not doing well then they may need to be stimulated to get breathing properly. Our girl just had a litter of 15 puppies 2 weeks ago, we only had to help one puppy, we just held him and rubbed his chest to get his lungs going and he was fine
As I said I have no experience with a chow, some breeds tend to be fantastic mothers and need very little help but others can be hopeless mothers who will ignore their puppies