15 - 30 minutes
After a good 2 years the juice ran out of my battery. I was having to plug in my phone every few hours to refuel!
Went well for someone who didn't know what they were doing. I had to take it apart twice though because I forgot to clean a little piece which caused some interference in my service. But other than that and dealing with a few stripped screws, it was a success.
Don't forgot to clean the part that it says on the guide otherwise you will be taking everything apart again. Also be gentle with the screwdriver. I stripped two screws in the process which made it very tough to get the back off. That sucked! It took about 30 minutes to get the back off the second time.