Er, dunno about the tea thing :P but in general it would be quite straightforward converting OldVamp to NewVamp (no experience with the other games). Bearing in mind that there's no metaplot (you can make your own if needed) and a different character-type configuration (13 clans vs 5 clans/5 covenants), it would take a bit of fiddling.
The mechanics are a little different too, just check out the different character sheets for example. There are several small changes, like a better combat system and successes being 8 and above instead of 7; but broadly speaking it's pretty damn similar. Same dice, same skill+attribute rolls, similar disciplines and so on. If you surf the White Wolf forums you'll find lots of pedants elaborating on these questions, so your best bet is to check there.
But, in essence, conversion is very possible. :)