apt-get upgrade 32-bit workstation to 64-bit?

[RalfGesellensetter <rgx@gmx.de>]

Dear list,

on a brand new 64-bit machine, I started with a Debian Edu Lenny workstation
image (no LVM of course), that contains some manual tweaks like java installations.

Hence, and because the install deadline is straight ahead, I dare not
start from scratch with a 64-bit installation. But I consider an apt-get upgrade
to 64 bit, if this is possible. 

To do so, I had to change the arch settings, somewhere?

Our CPU is some Athlon X2 64bit with 3.2 GB RAM. Is it worth to upgrade
at least the kernel to 64 bit or even the whole system?

Thanks for any enlightment,
regards
Ralf