First - listen to your surgeon! I am not a doctor and have no training as such. Anything I post is merely experience talking and I do not pretend otherwise.
After that, drink SMALL amounts of Water - sip don't guzzle - it will HURT
Chew every single thing you put in your mouth until there is nothing left.
Remember, Protein first - always
Do not drink 1/2 hour before or after you eat. Why? Before-it will fill you up faster and you won't be able to get the required amount of Protein. After - it will wash away the food you just ate and may have a "wave" effect, causing you to vomit.
Very hot or very cold anything may cause you to vomit.
Pain on your left side and left shoulder is PROBABLY gas - get yourself some GasX.
If you have eaten but think you want more food, wait 20 minutes and see if you are really hungry as opposed to head hunger.
I hope this gets you started. Good Luck!