Tomcat won't run EJB's, so you'd need to get an EJB container.
For that, I'd recommend
JBoss, just to see if you can get this app 'up and running'.
To move it to Tomcat, because that's what you're limited to, you're looking at replacing the EJB layer with another 'data access/business logic' layer.
That's either a huge task, or just a small one, depending on the complexity of the EJBs, and how well architected the original app was in the first place, and of course, on the size of the app.
If it's all of 5 EJBs, then it shouldn't take you too long.