You can find out all kinds of amazing things about computer hardware simply by finding some sort of identifying number on the component and punching it into Google. If you do not know the socket family of your new CPU, simply type in the model number that is stamped on the chip.
Next, I usually find the model number off the motherboard by looking around with a flashlight, which I then also type into Google. This usually leads me to the MB manufacturer's web page, from which the motherboard installation manual can usually be downloaded. Once this document is obtained, one can find the CPU's listed that are compatiable with the motherboard in it, and the information on what the socket family is there as well (or you can just continue to look with the flashlight, the socket number is printed on the CPU socket itself, usually seen slightly above the CPU). If you discover you have a compatable CPU in the same socket family, and it is listed in the MB documentation as acceptable for that board, after that, it is pretty simple, just plug it in and the MB should auto-detect the change.