Changing hardware

Hi All,
  I have done this with Windows machines but have never tried this with a
Linux box. How difficult is it and what problems will I run into or what can
I do to avoid problems if I want to change out my motherboard on my linux
box with another?

  I want to replace my K6 350 mHZ processor board with another. I may change
it with a 500 Athlon or purchase a PIII or P4 motherboard, I have a couple
of options open to me. It pretty much does everything I need it to do now
but eventually want to upgrade as this K6 is getting old.

Thanks.