Oleksandr: I would more ask, what is the reason on not having upgraded before! :-)
Janos: check the release notes and the documentation these are quite handy and give you additional information
(like if you use cdr's you would also need to back up these).
I think the easiest is to enable the FTP server and download all the files you find there.
To answer your questions:
Yes, it shall not be a problem to upgrade it.
The licenses should survive, though I would note down the option keys.
There is no release key needed for the new version.
The configuration shall still be ok, but I would go through all the parameters to look if everything
is still ok and check on the new parameters.
I would also do some testing and search for feedback by your users to see if the new features / changes
make them happy or bring in complications.
Like Sagar said, do not forget to make a backup. You would need that if you want to go back to the old version.
A backup should be done anyhow on a reoccurring base :-)
Martin
