It is an old phone but, because it uses the GSM system, it is usable in the USA with an international SIM card -- unlike my new iPhone 5. The original battery was no longer holding a charge, making the replacement necessary.
The job took me about 90 minutes, being extremely careful and methodical. The tool kit was appropriate. Good eyesight is required. The result was very pleasing for me and, when tested, the battery kept a 48 hour standby with something left.
My advice is to follow iFixit's procedure, as on their website. I used a large fridge magnet to hold the tiny screws in order when removed. Do remove the split ring from the suction cap as advised by iFixit; a rubber glove will give a more secure grip on the back of the suction cap and help prevent any sudden lack of control when pulling the screen away from the body of the phone. Being methodical is important.