Just done this and all went pretty well - hardest bit was the amazing tacky glue on back plate grabbing the new cable before i was ready, after one close call too many i put a sheet of the antistatic bag plastic over the gluey back plate and installed the cable. Once screws were in but not tight i removed the plastic sheet (which was a pita to get off anyway!) and pulled the cable backing off to remove even more adhesive!

If the power button replacement guide is rated 'difficult' then this fuller version should be too i suppose?

Phone all good afterwards, apart from plus volume button which seems a little loose - couldn't take that up with screw tension so assume its a manufacturing tolerance thing. Thanks iFixit :)