Guys, regarding assembly/disassembly and adhesives : RTFM !!!!
i'm posted link to instructions earlier : http://rghost.net/52107069
read instructions, watch videos and follow them STEP-BY-STEP to not end with torn out flex cables
regarding water-proof for z1 :
you MUST replace
Adhesive WP Cover Rear and Adhesive WP Window Back
however, if you have really talented hands, it is possible to reach testpoint in z1 without removing Rear Cover Assy.
in this case, only Adhesive WP Window Back should be changed.