Banner IVU Plus BCR - How do you replace a lens ? Any video's or drawings ?

Good Morning ,

I have a Banner IVU Plus BCR , that I need to replace a 4mm lens with a 8mm lens . How difficult is that ? Are you folks aware of any video's or drawings showing the procedure ? I searched YouTube , and googled it and really have found nothing on the subject . Have any of you done this before ?

Thanks so much for your help.

Page 9 of the manual shows an exploded view.

Found some lenses on eBay. This pic shows it's just threaded in.

Thanks , I should of figured that out.