Hi Gavin,
Having services on that vlan would not be an issue, however, you won't be able to remove a vlan (more specifically, the IP address of the circuit) as long as there are active content rules on it.
So, the steps would be first suspending all the content rules in that vlan (which I assume were already suspended after moving them to the ACE), then removing the IP from the circuit and finally, removing the vlan from the physical interface.
I hope this helps
Daniel