He would like to keep his AOL e-mail address if possible.
Do you mean he would like the same name for his Comcast account? Example, if he uses firstname.lastname@example.org he wants Comcast to be email@example.com?
If so, it all depends on whether or not the name is currently in use by another Comcast customer.
When Comcast internet is installed, he will have to create a primary account user name, which will also be his email address. He can try the name he wants; he will be informed if it is already in use.
If that's the case, he'll have to use another name.
If the primary account is set up under a different user name, he could create a secondary account using his aol name. Again, he will be informed if the name is in use.
Once that account is set up, all he has to do is log in with his user name to access webmail. There is nothing to set up.
What I suggest is that you give your friend the following link, it leads to the Comcast help forums which are provided to Comcast customers, and are a great resource for vendor specific issues. There are forums for computer issues, email issues, security, internet, cable tv, and CDV.
Many times we, the users there, can provide answers tech support and customer service can't.
Click the link below, you'll be sent to the sign in page. Log in with your Comcast user ID (the part before .net) and your password. You will next see a first time forum users page, asking you to choose a screen name for use in the forums. Once you set that up, you'll be taken to the actual forums. He can ask whatever questions he has about Comcast services. (He can't get to the forums until he gets hooked up to Comcast)
Link to Comcast help forums:http://forums.comcast.net/comcastsupport/
If he hasn't gotten connected with Comcast yet, he can still access the FAQ's for information:http://www.comcast.net/help/faq/
Account management has a section devoted to primary and secondary accounts-it will explain the difference between the two and he can find out how to create a secondary account.