How can a private pilot prepare for a long cross country flight in an unfamiliar area?
I'm in a similar boat to you and I just did my first XC from KDYL to KDDH a few months ago. Which was the first time I had been to an airport I did not go to during training. It was a lot of fun but here are a few things to consider, 

Get the G430 simulator as Ron mentions. You should always familiarize yourself with all systems in an aircraft before flying it. While you don't need to know the IFR capabilities of the 430 you should understand its VFR functions well. This video covers it well.

If you don't already use it, get ForeFlight or some similar app for your phone/tablet. This will provide you all the charts and calculations you need. Most pilots are using something like this these days but often times it's not allowed during training and many new pilots don't yet have it.   

Use flight following if you can. If your instructor never went over that ask a local CFI about what it is, how to get it, and why you should basically always use it when you can. 

Since it's a new airport for you, watch videos of others landing there to get an idea of what the terrain and airfield looks like. 

If you have, or can get access to a simulator, fly the flight in the simulator using the intended aircraft so you have an idea of time, and basic terrain features en route. 

Perhaps most importantly, this is no time to push your limits both physically and mechanically. Don't depart with "just enough fuel + minimums". Don't make this a "just above VFR minimum weather flight". You will most likely be flying a contiguous leg longer than you have flown yet, understand the human limitations in a situation like this. Understand that the plane has far more endurance than your body and understand when to say "I won't be making the flight today". 

Most importantly, Have FUN!