1 - 2 Stunden
no response at all from iPhone
The repair is not easy for unexperienced - but thanks to the fabulous step by step guide from IFIXIT - I managed and the iPhone is working again.
In any case - print the screw list and use a magnetic pad - I lost one tiny screw!
iFixit Opening Tool
iPhone 4 (GSM/AT&T) Power and Sensor Cable