Swap Bottom Bracket bearings or replace entire bottom bracket?
Without specially fitted tools, it is very difficult to install new bearings in a cartridge bottom bracket. Usually, the act of pressing the on to the BB spindle puts enough side load on the bearing to damage the new bearings. 

If you want to give it a try, yes, you can just go to your local bearing house and match the bearings by the numbers printed on the rubber seals. 

The normal procedure is to replace the cartridge, but the bearings are cheap, so it's worth a try, even if it's just to learn that it doesn't work out.