Blooming bike enthusiast needs beginners advice

Hi guys! I've been biking to school on my $100 wal-mart mountain bike every day for the past several years. I think I'm ready for that to change, and I need your advice.

In the past few days, I've been looking at these two things:
-Motors that can be installed on bicycles and switched to instead of pedaling.
-Trans-America bicycle courses with campgrounds along the way.

So, I've decided to buy a new bike and equip it with a motor, then go on an expedition across the bike paths of the U.S. next summer (I don't know if there are any purists here who frown on the motors... but I want to cover lots of distance, and I only plan on using the motor about 1/5th of the time) My only problem is that my passion for cycling has only been around for a few days. I don't know much about bikes, or what I should buy.

Here are things I want in a bike:
-Compatible with the motor kits.
-Good for riding through town to school every day.
-Good for long-distance touring (I.E. hooks for hanging bags and packs if needed)

I don't have a huge budget. I don't want to spend more than 400 or 500 on the bike if possible. I live near the Recycled Cycles store in Fort Collins, Colorado, so a used bike is definitely an option for me.

What I need from you: What should I buy? I don't know much of the terminology, so it would be so helpful if you could illustrate your post with pictures or examples of what you mean. I'm going to the cycle shop sometime this week, and I need to know exactly what to look for, and how to tell it's what I'm looking for.

Thanks in advanced to anyone who replies!