[Zope] Upgrading Zope

Hi All, I've been asked to migrate an ancient Zope server from 2.1.x to the latest 2.x or 3.x version. This server only have a couple of applications, both using Z SQL Methods, DHTML methods and documents, some products and some external methods. They don't use ZPT or Script (python) at all. I'd like to know if you think that such migration is feasible or if I'll encounter some problems. Do you think it is better to migrate to the latest version of the 2.x or 3.x branch? If you have any link on this subject is really appreciated. Bye, Andrew.