Normally the Crohn's is under control, purely by use of diet, and following two operations in 2011. That control is only through a restrictive diet, and I do still experience problems like the acid reflux from time to time. Azathioprine is the reason I have diabetes, it gave me pancreatitis.
Overall, I found it had a horrendous effect to on me, but that's the thing, no one knows how any individual will respond to medications. I later found out that azathioprine was never issued with a licence for use with Crohn's, but is used anyway. I don't know if your doctor has told you, because it's common for them not to, but it's not recommended to be on aza for longer than approximately five years because of the effect it has on the immune system, and then a 'holiday' is needed. The thing about needing to cover up in the sun and be careful of bacteria/infections actually brought out OCD in me as well.
Hopefully things go well for you though, but it's best to be aware of all of it.