Nutritional help for Crohn's

My brother-in-law is 36 years old and about to under go his first surgery for two severe strictures in his colon.  He also has kidney stones and is scheduled to have his gall bladder removed due to gallstones.   He smokes, drinks fake ice and believes his diet has nothing to do with the way he's feeling.  
I know nutrition has a great deal with how he's feeling and whether or not he will make to the age of 50.   I know he needs to cut out the sugar but what is the most important foods he should start introducing into his diet?
Thank you.  

[melissw]

i have ulcerative colitis, so i don't know know about a good diet for the gallstones and kidney stones...

but for me, salmon (baked or steamed, not fried) always seems to make me feel better.  all of that omega 3.
also steamed easily digestible vegetables (without skin), like zucchini, carrots.

vegetable juices may be helpful to get nutrients in...

definitely limit sugar, avoid alcohol and caffeine

good luck.