There's two basic ways that lenses of any real quality are held in an assembly - rings that require a spanning wrench and rings hidden behind covers that unscrew after removal of setscrews. Supercheap lenses may be pressfit into place, usually on plastic supports and the only way on those is to cut the support without damaging the lens. I might remind you to measure exactly what the distances from one lens to another is because the prescription is quite exact in order to get the right abberation corrections. Measuring to .0001 is usually good enough to start with.