[shrek]

I have a few G4 laptops with worn out batteries that need a rebuild with fresh cells. I'm a tad nervous about soldering directly to the terminals but I think it'll be okay as long as I don't keep the iron on it too long. 

Can someone who knows what they're doing give me a little help with purchasing parts? I don't know anything about batteries. Is it okay to use the highest capacity batteries I can buy or should I try to match the originals? What other specs should I look for?