another 'which cpu' please

[Omega]

Hi all, I have an ACER Aspire T120 with Athlon AMD XP 2400+ PCU on Motherboard: 11/04/2003-KM400-8235-6A6LYE1BC-00.
1/ What is the best cpu that I can upgrade to without too much trouble ? (I'm not a gamer or do lots of imaging)
2/ Is it a job that anyone can do ? I don't mind the mechanical bits,,, but am limited in the technical bit !?!?) I am having to replace the cooler at the moment, so could get a cpu whilst i'm at it.
Is it just a case of taking the old one out & putting the new one in,,,, or does one need to change bios or anything ?
Sorry for basic questions.
thanks
Omega