http://software-lupe.de/sl-tutorials/42 ... n-tutorial
It describes 4 update options:
- automated update using extensions manager (requires PHP allow_url_fopen = 1)
- package upload and "install" function of the extensions manager
- ftp package upload and "install from directory" function of the extensions manager
- ftp files into joomla directory
And it addresses some issues that you might be left with (like missing version info in the footer).
Unfortunately I do not have the time to translate it just now.
If you understand some German, you may find your way through.
If no english version turns up until the weekend I will contact the original Author (Lintzy in the German joomlaportal.de Forum - all credits have to go to her!) and try to work something out.