hi carl
first off, congrats! you're in for a hell of a ride.
secondly, for the liquid portion of your diet you really want to stick only to the liquids. It will help not only clean your dietary tract for surgery, but the liquids will also help all the fat and toxins out of the body if you're ... releasing more of them.
It is a low calorie, low fat, low.. everything kinda diet for a good reason. You need for your body to burn off as much of the fat from your liver as humanly possible before the surgery. At my size (31.7 st) at surgery, my liver was still incredibly large and difficult to perform the surgery around. I had lost 1.2st during my 2 week liquid diet. Anything you can do now will greatly improve the weight loss prior to that.
My own personal recomendation if you wanted to start early... have 2 liquid meals a day and a SMALL sensible dinner in the evening. By small.. 2-3 ounces of lean meat, 1-2 servings of vegetables. Try not to eat the grains, even if whole grains (that sammich every other day has a LOT with 2 slices of bread). Drink drink.. and then drink some more water or iced tea. Stay away from any sugary drinks or carbonation if you need to wean yourself. Same thing goes for alcohol. Its empty calories, do yourself a favor and avoid them.
Keep us updated on your progress!