Kubuntu - AMD 64 bit installation newbness

[Donn]

Hello all (take 2 - I'm new to Thunderbird),
After my recent mother(ed)board meltdown, I have been forced to join the
21st Century and get new stuff. A friend helped me get the parts at just
about cost, so that helped. Anyway, the thing: It's an AMD Athlon 64bit
CPU (X2) and I have no idea how to .. well anything with 64 bit.

1. Can I boot off my previous machine's hard drive? It had Kubu Dapper
i386 installed (assuming my drives didn't go bang too ...) Will the i386
version run just like that? Do I have to do some BIOS footwork?

2. If I decide to go for it and install a 64 bit Kubuntu, is it on the
original Dapper install CD, or do I have to fetch a special .iso file?

3. Can I run 32bit apps from the repos? I mean I don't know how far the
64bit compiling has gone. Is KDE in a 64bit version, or is it only the
kernel that goes 64 while the apps kinda catch-up randomly?

4. I guess I just am totally unsure about which repos to use and if they
can be mixed.

So, any suggestions. I really hope I have not goofed with the
chip-choice. I might have a day to change the order still ...

/d