Bicycle Mechanics - new to road bikes - need modification help! :]

I've been snooping around the forums for a few days and I've decided that I need to just ask the question I've got, and hope I get an answer.
I'm sixteen, and I've signed up for the "America by Bicycle" ride, from St. Joseph, MO to Portsmouth, NH ride. I'm in great shape - I swim, I run, and I bike a little - but I need to do some serious training for this as each day is going to be 80-100 miles. I just bought a bike - a new mercier corvus

Frame Reynolds 520 double-butted High Grade Steel with eyelets & rack braze-ons
Fork Reynolds Ouzo Comp Carbon Fiber / Aluminum Steerer
Headset FSA Threadless for Cane Creek
Crankset Truvativ IsoFlow triple 52/42/30T
Bottom Bracket Truvativ sealed
Pedals Alloy Road with Toe Clips and Straps
Front Derailleur Shimano 4400 for Triple
Rear Derailleur Shimano NEW 105 for Triple
Shifters Shimano 4400 for 27-speed
Cassette/Freewheel Shimano 9-speed 12-25T
Chain Z-9000
Hubs Formula Aluminum Black, sealed bearings
Spokes Stainless Steel
Rims ALEX DA-22 Aluminum double-wall black anodized with machined braking surface
Tires Kenda Racing 700x23c
Brakes Aluminum Dual Pivot
Brake Levers Shimano 4400 STI
Handlebar Ergo Butted Aluminum 6061
Stem Aluminum Threadless
Tape/Grip Cork
Saddle Velo Racing
Seat Post Aluminum Micro-Adjust

And I was told by my grandfather (who did this ride a few years ago, and who is going with me) that I needed a 12-30 rear cassette. I asked the woman who built the bike and who was selling it to me if the dérailleur could handle the 30 tooth cog, and she said it could, but that I might need to change the crank. I'm not sure what I would need to do/buy to put a 12-30 cassette on my bike. I am very good with my hands - I build battlebots, and I have a lot of experience with building things and working with metal - so I could probably make the necessary changes myself (if there ever are any).

Can someone please help me out? This is my first road bike, so I am not familiar with all the terminology and technical jargon that a lot of people use when giving advice, so simple language would be appreciated. :]

Thanks so much

http://www.parktool.com/repair_help/FAQindex.shtml and http://www.sheldonbrown.com/articles.html will tell ypu how. Change the cassette to a 13/30. You may need a new chain to get a few more links, a SRAM or Wipperman with a replacable master link is a lot easier to deal with than the Shimano chain. 25 mm tires will be more comfortable for riding these distances, but the current ones will do while you are training. Shimano A520 pedals are great for touring as they have a platform to provide extra suppotrt for the foot, and they can be worn with SPD shoes which you can walk in. Ask you grandfather what he thinks of these suggestions.

Another option would be a 48/38/28 trekking (touring) crankset. Nashbar has one that is ISIS splined.

1. Are you sure that you heard your grandfather right? That's not a stock 9-speed cassette. Shimano road cassettes usually end at 27 teeth and Shimano mountain cassettes end with 32 or 34 teeth.

2. To change your cassette you'll need a cassette lock ring tool, a chain whip, and a big crescent wrench.

3. You can almost never change just one part on a bicycle because everything works together. In this case you should probably get a new slightly longer chain. The rear derailleur that you have will probably work with a 30 tooth big cog but will probably need to be replaced with a mountain bike rear derailleur with a 32 or 34 tooth big cog.

4. Your bike shop lady was probably suggesting that, insted of messing with your cassette, you replace the 30 tooth front chainring with a smaller one. That would almost certainly be cheaper, would still give you the easier hill climb gear, and would eliminate the big steps between gears for the flatter majority of your riding. That's what I would do too.

The largest rear cog a 105 r der is rated at is a 27tooth. You could go to a mtn der and be fine put on a deore and a mtn 11-30 cassette and your set.

I have a 48-36-26 crankset and it's great. With a Sram 12-26 cassette, I have a 1:1 gear ratio.

Looking at the specs of the bike, I would look carefully at the following components:

Alex DA-22 rims can be problematic. I had a 36 spoke rear that started breaking spokes soon after I got it. At the very least, have them trued and tensioned by a shop as soon as you can. Think about a more beefy rear wheel, especially if you'll be carrying any kind of load or weigh more than jockey.

23mm tires are very narrow. Too narrow if you will be carrying gear. 28mm tires are much better.

Lastly, if you have any problems with your butt hurting after a long ride, Brooks B-17 saddles are the gold standard for touring.