I tried taping the side buttons on but they slipped out anyway.  Observe the photo to replace them in the proper orientation.  It’s actually quite easy, and I’m not certain how effective taping them would ultimately be as it’s important to seat the slots over the tabs inside the body.  You need to be an extraordinary taper to stick them in place such that they “presto!” drop in place when reinstalling the mainframe

I’m pretty OCD and wanted to reuse the plastic bag, but when I pulled if off it got all twisted up, so I just tossed it.  The instructions are correct that it is not necessary for normal operation - my phone worked just fine without it.

This may seem silly, but I’d suggest inking an X on the old battery and setting it aside a good distance from your project when you remove it so you don’t get it mixed up with the new battery!

It took me over an hour to pry the back cover off the phone.   Don't give up – it can be done!  It takes some time, heat, and persistence to wedge the blue picks under the back.  And not knowing what is under there can cause stress!  Bottom line - don't be afraid to apply pressure to the pick to break the seal between the back and the metal edge, and then you can slide the pick in under the back cover without breaking any electronics.  I did not notice the blue plastic prying tool until after I wrestled the back off – I think that would have helped with the final peeling off stage.