The lens is very easy to change. Simply twist the retaining ring (nearest the camera body) WHILE HOLDING THE LENS and then the lens should come off. (Beware this move as some people mistake the retaining ring for the focus ring and cause the lens to drop on the floor!). Don't touch anything when the lens is off and keep it clean, dry and dust free. Install the wide angle lens and tighten the retaining ring.
Calibration of cameras is typically done with each lens on the camera so, to be in calibration, the camera and the lens would need to go back to FLIR. You will need to decide if you can use an uncalibrated camera or not. Worst case it could be out of specification if not calibrated. Best case, it would be accurate but you would not have a certificate of calibration.
Thermally Yours,
John
ASNT NDT Level III #48166
The Snell Group
www.thesnellgroup.com
www.thermalsolutions.org
800-636-9820