Yes, remove that battery as quickly as possible and clean the board with a solution to neutralize the decomposing battery "Fuzz" from spreading further and continuing to cause damage to the motherboard even after the battery is removed.
Check the Internet for how to prepare a neutralizing solution. You can probably max out your motherboard RAM by contacting AmigaKit in the UK. If they don't have the RAM in stock, they can get it for you. Maximum RAM you can install on the motherboard is 2mb Chip RAM and 16mb Fast RAM. Since you have a Cyberstorm Mk2, you would be better off to put your Fast RAM on it instead of the motherboard. It can take up to 128mb of Fast RAM.
