I hope you have LOTS of time because Disney World Resort is MUCH bigger. There are four parks (one world) and lots of other attractions like Downtown Disney, the water parks, the campground, golfing, etc.
The best prices for tickets are military, then other organizations like AAA. Disney is trying to crack down on the "side of the road" sellers and may or may not let you in with those tickets. You can also get free tickets if you sit through a timeshare sales pitch.
Staying on Disney property also gives you special prices and hours.
Plan on just one park per day unless you're going to return to that park another day. Get the free DVD and visit planner.
The weather in Florida tends to be hot and humid, so plan accordingly for that. Pace yourself. Don't rush. Like JoMerr said, it's a huge place, so don't try and see everything there; if you do, you'll just burn yourself out and not have fun.
If your time is limited, I would plan carefully and try and skip things that you've already seen at DL. Check out Disney.com and allearsnet.com for info regarding like attractions.
Most of all, have fun and post a trip report here when you get back!
One question, How long are you going to stay? There are more opportunities to get lower priced tickets the longer you stay. If you are going to stay over a week, you might consider getting an AP. With an AP you can get discounts for hotel stay. The extra cost might make up the difference in price.
If you want just entrance only tickets, then you have to decide if you want to park hop, if you want the tickets to expire, and so on. There are ticket outlets that will give a modest discount if the trip is long enough.
Jiminy Cricket Fan
You should have a blast. As mentioned, if you're going more than five days and are staying at a WDW resort, an annual pass might actually be the best financial deal. Worth checking out in any case. If you're staying at a WDW resort, do the Extra Magic Hours in the evenings after the parks close (one park is open up to three hours past closing on certain days of the week exclusively to resort guests). Pace yourself and take breaks when you need to rest. It really is a huge place and you can wear yourself out if you don't pace yourself.
Warning: Portions of this attraction are intense and may not be appropriate for younger children.