New bee on portals and portlets development

Hi,
I just started to think about representing the information using portlets and portals. I have the following question before proceeding to work with portlets

a) Do we need any special server to deploy portlets? I have come across the term portlet container? Does this mean that we need to deploy portlets on a portlet container rather than web or application containers. the reason for asking this question arises because, I have an existing application which was built using Struts,EJB ,hibernate and deployed on an application server like Jboss. Now i wanted to use portlets in this application.

Is it possible to replace existing jsps with portlets.

It would be great if some one could throw light on the above question

Thanks,
Shyam.

On the similar line, I had a few question about the portlet deployment.

How do I deploy my portal application:
# through the Admin console on the Admin Server?
# through the WPS administration console?

What is the use of the utility xmlaccess.bat? Is it that by using this utility we needn't deploy the application through WPS administration console?

Can some one please share a detailed example as I am not able to get a clear idea from the urls available over the internet?

Thanks in Advance.
Vicky