I hate to say it this way without sounding like a cliché, but just take it one event at a time. Focus on your your race plan at the start of each race and then reset when getting ready for the next one.
One track meet a long, long time ago, I had to fill in for the 3200 relay, then run the hurdles next. It wasn't that bad, but I know that swimming is a lot different.
Good luck and let us know how you do.