Eben Ostby posted step-by-step disassembly instructions, with photos, for the Lex 35/Vivitar T100 toy camera. Check it out in this thread in the Trashcams group on Flickr.
Lest you be tempted to splurge for the Vivitar T100 for US $7.50, be aware that it’s the same camera as the Lex 35 except that it has a tripod mount and says Vivitar on the front. While I don’t think that’s worth the extra 6 bucks, it does mean that Eben’s instructions apply to it as well.
The Lex 35 is available for a whopping US $1.50 from American Science & Surplus in the Optics -> Optical Devices section. (Sorry, can’t link directly.)