The three tools joejack mentioned will set you back about $35. Size the new chain to end up with the same number of links as the old. If you do a lot of hill climbing, you might like the cassette with the 32 teeth; if you ride mostly on level, choose the 12-26. I am making the same upgrades on my FCR3 with 2900 miles. Both the chain and cassette had significant wear. The Sram 850 chain and cassette represent a grade up from the original components, so they should have improved longevity. If you wish to stay with the original gearing, Niagara Cycle Works has the Sram SG-850, 11-28, cassette for $22.