You did not post what type of bottom bracket you currently have. Assuming that it is a cup and bearing type, it could just need a fairly simple adjustment. If you want to upgrade to a cartridge type bottom bracket (bombproof), you need to remove the crankarms and find out what the spindle width is and order a cartridge bottom bracket that is the same width. You will also need A) lockring tool B) Fixed cup removing tool C) Splined cartridge bb tool. D) Crank removing tool. E) tool for removing the crank arm bolts- either a 14mm socket or 8mm allen key.