Inst. J2ee on exist was6.2

We have an ides system that I want to install the j2ee engine for (ides 4.7) I downloaded the current manual and there is a section on adding j2ee server to existing central instance.

Basically it asks for reloading the sapinst software from the original CDs, but is this really necessary or can I just do a "prepare a new install" from the existing menu?

What is the basic steps for doing this?

Also the R/3 User SAPJ2 (or something like that) already exists in IDES but I can't find the password in any documentation - can someone point me to it, or can I just change it myself. I read that the install will ask for this password.

Thanks