conversion of an installed base i386 -> amd64

I have finally decided that I really should have installed my 
quad-core-2 equipped box as a amd64, instead of the i386 (32 bit should 
have been 64 bit).  I just finished a buildworld, and I checked, the 
binaries (which I haven't yet done an installworld on) are actually 
amd64/64 bit binaries.  I'm running -current, which is mostly why I;m on 
this list, but my question is one of installation order: in doing the 
conversion, I don't really like the idea of accidentally hanging the 
box.  I would like someone to please let me know, what's next? 
Understand, I am still running the i386 compiler (but the buildworld 
builds it's own private compiler, thank you very much).  I need to know, 
should I install the world next?  Or, is there some more correct 
strategy to get the kernel built?

Understand, I'm running a 3ware raid, and while I got that in position, 
to make me feel really safe, i installed the system first  in a 
junk-pile EIDE drive I happened to have laying about, so I actually do 
have a emergency drive I can quite easily boot from, if some disaster 
happens.  I've tried it, it serves me as a very safe backup right now. 
So, I don't need to worry TOO MUCH about a disaster, but I would like to 
avoid it as much as I could anyhow.

Thanks.