Upgrading Cpu & Mobo

I have a couple of questions regarding upgrading my set-up to A64, I'd appreciate any input anyone has.

First my current set up is:

AMD XP2600+ OC'd
EPoX 8KRA2
512Mb Kingmax PC3200 DDR memory
80Gb Maxtor DiamondMax9 w/ Win2K Pro
nVidia FX5200 256Mb

Dvd drive, Cd-RW, FDD etc.

Basically I've come across an upgrade package for €315 which has:

AMD 64 3000+ (S939)
EPoX EP-9NDA3+ nForce3 Ultra
512Mb Crucial memory

I've read reviews and I'm happy enough to stick with AGP on the nForce3 instead of PCI-E on the nForce4 (Due to a pretty tight budget) and I'm happy with the other features on the mobo.

What I'd like to do is get the upgrade kit and take out my current Xp2600 and mobo and simply replace them with the new ones.

First question is; Will I be able to do this or will the OS not run properly with the new set-up? Keeping in mind that I don't want to format my HDD if at all possible.

Second; The 64-bit 3000+ has a lower clock speed than my 32-bit 2600+, does this make a difference in speed or will the 3000+ be faster because it's 64-bit?

Lastly; If anyone has any other suggestions for a different set-up or anything I should do different I'm all ears.

Hope you guys can help me out.

Ross