Post some detailed photos of your bottom bracket.
The Shimano bottom brackets I have don't appear to be easy to disassemble.
Other brands such as Interloc racing appear to be easy to replace the bearings in. Most cartridge bearings will have writing on the sides indicating the size which any bearing store should be able to cross reference.
This popped up with a quick internet search.
Campagnolo Chorus Ultra Torque Bottom Bracket Bearing Bicycle Bearings