I did it, thanks to you guys! Had to change the backcover, the power button and the mute button of an IPhone 3GS and thanks to you it was a success. Struggled a few times. Took me a long time to detach the battery from the old backcover. And the end of the disassembly there are a few steps missing in the tutorial since I had to transplant every little bit in the new backcover but I figured it out. When reassembling, steps 22-20 almost made me cry - $*&! mute button! Now the phone can be used again although some buttons do not work that good (tactile feedback is missing on the power and the volume buttons). By the way: it took me almost six hours to take the phone apart and put it back together. I'm still happy!