Desktop Service Organizational structure balance

I am in charge of a large desktop end user population. I need to structure my organization to balance break/fix with projects for new hardware implementation and moving to a standardized managed operating system.

As most of state government these days we have limited resources to task with this workload. We are working with the Planning groups to better manage the timelines and client expectations.

If anyone has any models or can point me in the direction of some publications that can help me I would appreciate it.