I work for a company that produces enterprise applications to be used by schools and districts to manage all of their tests and standards data. Their existing application is written in J2EE and is very large. I personally am a seasoned PHP and Ruby = RoR developer and I have been asked to attempt to implement easily added but crucial features to an existing J2EE codebase. I am very familiar with Java SE and know the architecture of a web application well.

What I am asking for is, will this suffice for the task ahead and what tips can you give me in digging into the code base and actually efficiently adding these new features? Is there anything important I need to know before beginning and what can I expect in terms of problems and issues coming from a Java SE, PHP, RoR background?

Time isn't too much of an issue, I should have plenty of time to familiarize myself with J2EE.Please also note, syntax will not be a problem here.