All fine !

我的问题

As for many users, my 3GS ran out of battery too easily and often, and I was fed up by Apple's repair costs...

我的修理方法

I was worrying about such an operation, but following carefully your guide step by step, I didn't encounter any serious issue. Just kept my cats from jumping over the table where all these small parts where lying ;-)

我的建议

Take it slowly, and try to avoid any disturbance. It's so easy to break a small part, or to forget connecting something...