I'm not a big fan of the shake diet. It's not sustainable for the rest of your life.
That being said, I now and then, have a protein shake. Simply because of my work and weight lifting schedule/timing, and I need something fast to replenish and stave off raging hunger.
So, a couple of thoughts.
Being 6 weeks post baby, I would not make any huge choices right now regarding surgery. Most likely, you are very hormonal and exhausted!

Been there done that.
I hate the word diet!
It's not a diet, it's a lifestyle change. It takes time to do the research, learn your body, learn to like healthy food, and actually find recipes that make healthy food taste good!
It takes time for your mind to get around to the fact, that most likely, you will always have to keep some kind of track, be it calories or WW points or whatever and always be mindful of your eating.
This does not mean you can never have a Whopper, or pumpkin pie at Christmas, or a ribs at a bbq, you just can't do it every day.
Personally, I could not live the rest of my life, drinking 2 shakes a day and one meal. I like food too much!
However, after many years of trial and error, I've figured out what works for me and I have tons of go to foods, and recipes! Some boring, some great!
I also allow for/work into my plan things like weddings, holidays, birthdays and so on.
Cut back a bit for a day or 2 and up my activity a bit for a few days! Portion control, don't beat myself over the head for one piece of cake or pie.