We'd our very own custom web server(designed in java) built-in 2005. We are thinking about moving to apache web server. Does anybody know any pointers relating to this process?

What's your code base in? Whether it's also in java then you may need a middle layer to really run your programs, like tomcat.

Why would you like to proceed to apache. For any java code base you'll be adding a layer of complexity. However, should you current server is damaged or otherwise scalable then go ahead and switch.

Here's articles on establishing tomcat and apache.