It will be busy, but as long as you plan for it and are prepared to wait, you will be ok. Look at the website, and decide ahead of time what you want to do. The shows will fill up quickly, and may close before the start time (The Sea Lion and Otter show does this on a regular basis), so plan on being at the shows you want to see early. My favorite restaurant is the Ship Wreck Cafe, and DO NOT hit this one after a Shamu Show, and the lines will not be too bad.
Navigating Sea World is not that bad. I would look at the online map, and get a feel for it.