Custom Kernel installing is not a matter of joke, if u will do anything wrong it may lead u to a mess..... Generally, kernel up gradation/ replace default kernel is the matter if there is any new HW is considered ! if this is really necessary for u, it is better to do the job first on any test PC and after getting success, implement the same on the production machine. However, u can navigate here for procedure:
http://www.linuxchix.org/content/courses/kernel_hacking/lesson4