Changing the battery in a Super Famicom cart

[Arctic Feather]

I've got a couple of Super Famicom games whose batteries seem to have died 

I now I'll need a special screwdriver to open the carts, but once I get them open is changing the battery straight forward or will it require some soldering?

Also which batteries will I need to buy to replace it?

[famiac]

I replace batteries if you are located in the US. Shoot me a pm.

[Algo Fonix]

I've seen people say the non-solder methods are good... but I don't trust that at all. If you can get someone to do it the right way, or do it yourself you'll be much better off.

[Arctic Feather]

I replace batteries if you are located in the US. Shoot me a pm.

Thanks, but I'm in Japan.

I'll probably give it a go myself at some point, but I don't even have a soldering iron at the moment so it will have to wait.