Your gonna want a steel gear. Summit sells em. You CAN use a bronze gear, but it will wear out over time. THe gear on the cam is steel, so your gonna want a steel dist gear, instead of the softer bronze gear.
To get the gear on/ off is actually really easy. Your gonna wanna pop the single pin out that is holding the gear from spinning. Now, take some channel lock pliers and rest them over the gear without gripping the shaft. Put the dist on a piece of wood and bang on the pliers, the gear should slide off without much trouble.
To get the new gear on, just use a huge socket that will slide over the shaft and bang the gear into place. You will need to drill one hole into the new steel gear, since it only comes with one hole and you need the second for the pin to hold it in place.
Its all very easy and shouldnt take you more then 15 minutes.