I've not heard of anyone being asked to do a medical in order to get married! I certainly wasn't required to do one.

What do you mean about the hukou? Presumbly she has one as she's a Chinese citizen but all you should need is your passport as well as a certificate from your own embassy stating that you are not already married and possibly official documents to show you have been divorced where necessary.

You should check with your embassy what is required and then check with the authorities where her hukou is registered. If your soon to be wife is from a small town or city then it's likely that they won't be able to register the marriage between a Chinese and a non-Chinese and therefore you'll have to go to a nearby big city to carry out the procedure.

In general and in comparison with other procedures in China registering a marriage is easy!