well before starting to run you must learn to walk ehhheheh :-)
Jokes apart, it depends on how much you are skilled on JEE technology.
Seam is a quite useful framework but it assumes that you are familiar with concepts like EJB and JSF. So I'd suggest ai first to learn EJB 3.0 and JSF.
Then you can move to framwork like Seam and JBPM, it will be much easier.
Hope it can helps