Any time you replace an AP with an controller and AirWave, you should do so using the following steps.
First, make sure the AP is down. If the AP is being replaced because it is not working, this will be obvious. If the AP is being replaced because you are replacing it with a newer model AP, bring it down.
Connect the new AP to the network and from the controller or MM (OS8) and assign it the exact same AP name and group as the one it is replacing. When the AP reboots, it should connect to the controller and essentially become the AP that it is replacing. At this point the AP is up on the controller, however AirWave knows devices by their MAC addresses, not their names, so you need to proceed and replace the old AP with the new one in AirWave.
From AirWave, find the the down AP and select it. You should see the Monitor screen for that AP. On the menu to the left, choose the Manage menu. At the bottom of the screen that appears, you will see and click on the Replace Hardware button. From the New Devices section, select the new AP (the new AP was discovered and added to the New Devices category automatically when the controller was polled, but since you didn't [hopefully didn't] add the AP to AirWave yet, it is now able to be selected) and replace the old one with the new one.
At this point the new AP should be in AirWave and should have replaced the old AP. All of the historical data from the old AP has been unlinked from the MAC address of the replaced AP and linked to the MAC address of the new AP.
I hope this helps,