Why do you think you need a new BB? Chances are you can take the one you have apart, clean and repack it and be good.
If you need a new BB, then you will need to take the old one apart and measure the width of the spindle (not including any threads) as well as the distance between the cones and the length of each shaft end. From these measurements, you *might* be able to find a replacement. If you need new cups, you will need to get the right threading for your BB shell. Be aware that the drive side cup is probably reverse threaded.
Getting the BB apart and reinstalling it requires a crank puller, a spanner wrench for the left side lockring, and a pin spanner to hold the left side cup for tightening and adjusting. If you need to remove the drive side cup, you will need a big wrench or special tool to fit the flats on the cup. If you just need to repack the bearings, you do not need to remove the drive side cup.