Lens replacement is simple.
1. Front cover unscrews. Dont lose the O-Ring when taking off..
2. Look for the little set screw and loosen sufficiently for lens to turn. (I will include a free set of screw drivers if you need)
3. Remove and replace the lens with the desired focal length. turning the lens until it comes into focus.
note* Sometimes when tightening, the lens will shift a little and you may lose the perfect focus.. just re-adjust and hold the lens while tightening to solve this.