thinking of converting from band to sleeve.

I'm considering removing my band for various reasons. My BMI is 32. If I'm having issues with it will insurance cover a revision to sleeve? I have severe sleep apnea and diabetes 

Maybe, maybe not. First check your coverage - some policies only cover one WLS. Also, your BMI may not be high enough, even with sleep apnea and diabetes.  Most policies require a BMI of at least 35.  Also, if your band itself is not causing any physical problems, they may not cover a "revision".