Bicycle Mechanics - Adding a granny gear?

I have an '04 P.2 and I want to add a granny gear and a bashguard. Can I just buy the gear and bashguard, or will I have to buy the whole thing (http://pic10.picturetrail.com/VOL326/815976/1747806/66023746.jpg)? The P.2 comes with the Truvativ Hussefelt crankset, but with just 1 38t chainring. Thanks.

Depends on the crankset. If the ring is bolted not rivited to the crank arm you should just be able to undo the bolts and fit a bash guard. As it currently has only one ring the bolts might not be long enough so you may need a longer set.
You will be able to fit a granny if the crankset has the threaded holes for the bolts.
Your current chain guide will no doubt not work with two rings so if you need a guide be prepared to replace it with a duel ring version eg e.thirteen drs (http://www.e13components.com/drs.html)

along with your allen key (hex key) you'll also need the chainring bolt tool. It's itty bitty and cheap, but necessary for installing that bash guard. For a granny you don't need it though.

Thanks for the help. My crankset doesn't have holes for a granny, so I had to get a new one, along with an e.13 DRS.