[CentOS] Upgrading kernel

So here's my questions.

1.
If I install Kernel manually (downloading latest kernel), is the .config 
file on my disc and can I use it so my starting point is the setup for 
this pc?
Is this the one? /usr/src/kernels/2.6.9-11.EL-i686/.config

2.
There is a routine for upgrading a upgraded kernel with the rpm tool, is 
it available a upgraded kernel for Centos 4.1 or can I use latest fedora 
kernel?

3.
I read some place how to make a kernel the rh way or something (making a 
rh kernel from the kernel.org kernel) Has someone a good routine for this?

Small pointers and links would be appreciated.



Spec. and info

CentOS 4.1 – amd64 athlon s754
Linux localhost.localdomain 2.6.9-11.EL #1 Wed Jun 8 16:59:52 CDT 2005 
i686 athlon i386 GNU/Linux

I have been running 64bit and 32 bit back and forward a couple of times 
on my desktop and ended up going back to 32 bit. Even thou I now 32 bit 
programs run on 64 bit, I need Java fully supported.

My concern is that I believe that I visually can see some difference in 
performance and that the 64 bit seems to be a little more stable and 
faster. My impression nothing more, programs don't hang as long etc.

Therefore I would like to upgrade my Kernel to see if this will help me.

kai