Oh, a tethered jailbreak is a foolish thing to have.
I didn't like the concept going in.
But once I discovered what'd been done to this phone, that was my only option.
Never sign up for that on purpose!
The battery change wasn't that bad.
I spent about an hour doing it, and it was kinda relaxing (as opposed to nail-biting)
If you've changed out your screen, this is really just more of the same.
Eight (?) more little screws, several more fiddly connectors, and some wiggling to get things seated properly.
I did a youtube search with "3gs battery", and watched a dozen videos.
I'll recommend specific ones if you're about to dive in.
If you aren't careful what you're buying on Amazon, you could get the same (?) product from any of half-a-dozen vendors.
Are they identical? Not likely, based on reviews.
So far I haven't seen any rejection of this non-standard battery by the phone.
I went with this one from
Eforcity @ $3.89 + 2.98 shipping.
It has tools similar to the ones shown (two screwdrivers, plastic pry tool), and that's all I used.
Ordered Monday, and it arrived Friday, even in the midst of holiday mail.
I'm still in the middle of the first discharge cycle, so I really can't say much about the battery life.
I have about eight documented runs on the old battery, so give me a week to collect some data on this one.