Top be honest if you only know the CPU is bad because a friend told you and you are asking these questions then it may be best if you get someone to do it for you.
but in case you want to:
You need to find out what CPU are supported, to do this the best thing you could do is contact Sony to see if they will tell you which ones are compatible, if they won't you could google the model of laptop and see what otehr CPUS are being sold with it. Otherwise you could find out what motherboard and chipset it has and tehn do some reasearch to find out whichc CPUS are competiblem and then hope Sony havent restricted the chipset.
Once you get your CPU tehn teh funs starts!!!