Help - Replaced battery, still getting sad face

I ordered the kit to replace the battery for my ipod mini and it has made no difference. The ipod mini's problems have remained the same: the display rotates between 3 screens when it's plugged in or has a charge: apple symbol, then the battery symbol with the lightening bolt (battery appears to be 1/4 charged in the image), and then a picture of an ipod with a sad face overlaid with a "!" in a triangle, and at the bottom it says www.apple.com/support/ipod.

Since changing the battery, the ipod is making a buzzing/electronic noise you can hear when it's close to your face. Almost like the old dial-up sound.

My main goal is to get the music off of it onto my computer or another device. Second goal would be to make it usable because I think it's really fun and retro looking.

Thank you for any suggestions!