[TYPO3] Typo upgrade

[Nino]

Hi,

May i have some advice of experienced Typo3 users. I have to make an upgrade 
from Typo3 3.6.2 to 4.0.2. My 3.6.2 installation is using many old modules, 
specially tt_news (1.0.4 i think) and there are 5 different webs under it. 
Previously i had some upgrade attempts on some other installation which 
didn't go well so i'd like to know if this is mission impossible? Thx.

Regards,

Nino