I was in a similar situation as you. 47 years old, 340 lbs (down from 400+), and doing a physical job, playing basketball still, and enjoying life. Then the dreaded D word came up, and I'd seen the diabetic story play out too many times. WLS immediately went from the back of my mind to it's happening.
I picked the brain of a friend who'd had it, lurked on forums like this, and had 2 notebook pages of questions for my surgeon, and dietician. To answer your question, the liver shrinking diet prior to surgery tested my soul. Followed that up with the 3 week liquid diet post surgery. Was more bored than anything. Soft foods, on it now, and it's not hard, and extremely satisfying. Not only will you live on fewer calories, but with the proper preparation, the right mindset, and a good support system, you'll thrive.