2 - 5 minutos
Probably the number 1 or number 2 in repairs, right? Accidently dropped the phone and there ya have it. One panel, shattered to bits.
Now this is an easy one and happy it's not the front panel. This only takes removing the two bottom screws, removing the back panel. Putting the new back panel in place and (just to make sure) inserting new screws. Done! As good as new.
I would use new bottom screws every time they have been remove. Unless you are absolutely sure they still are in a perfect condition. Otherwise, replace them.