How to design SOA for EJB

Hi
My current application architecture is as follows

Frontend- Weblogic portal
Backend - EJB with Stored proceedure deployed in BEA Weblogic 7.0.

My customer now wants to move from vendor specific app server to open source framework.also they want to remove RMI.
So one of the architecture has recommended SOA based architecture.

Can any one give me the solution for how to approach this architecture.How to write specific wrapper class for EJB and what all design consideration I have to look for.
Also if you have any links then please let me know.

Thanks in advance.