Nausea & diarrhea can both be side effects from gallbladder surgery, the latter is a result of "dumping". Dumping refers to the "dumping" of bile into your system after eating fats; before your surgery the bile would be secreted through your gall bladder into your system to slowly process the fats. Now, without the gallbladder, the bile is dumped and the result are really quick trips to the bathroom.
With my surgery I was told to eat no or low fat meals, several small meals a day, instead of larger meals. Take a look at what you are eating, how often you are eating and how quickly you are eating. By adjusting your diet you may be able to work your way through the nausea and diarrhea. The more time that goes by, the more likely your system will adjust to the lack of a gallbladder.
As far as the pain on your left side is concerned, it may be the result of the diarrhea too, but from inflammation caused by it...that and gas. Appendicitis pain is felt in the lower right quadrant of your abdomen, not your left. If it continues, definitely see your doctor.
Hope this helps.