I definitely think there is enough material on SQL Agent to fill an hour. The only way to be sure is to write the presentation and then practice it. If you can do it between 40-60 minutes with no one around you'll probably have enough for an hour presentation. Remember that there will be questions.

For the abstract I think it is important to list 3 specific things you expect the attendees to learn from the presentation. For SQL Agent I'd do something like:

"After this presentation attendees will be able to:

1. Identify scenarios where SQL Agent should be used

2. Schedule jobs to run at selected times.

3. Define an operator to be alerted when a job fails.

"