Unfortunately I missed to take pictures of the disassembly of the Beroflex but at least some of a 400mm Albinar. 

To disassemble the lens you take off the front part and clamp it securely. Since the housing is not used anymore you don't have to worry about scratches. Only the lens must not be damaged.

Afterwards you carefully unscrew the front ring and the lens block with a screwdriver.

Before removing  the lens mark which side is front.