How do you know? Look at your POST screen when it first starts to see what BIOS version you have. Will be the first thing displayed on the screen, you can stop the POST screen by pressing the "pause" button on your keyboard if the screen disappears to fast to read it. Press "pause" again to resume POST. Then, go to the ASUS web site for your motherboard, and see if your BIOS version supports the new processor.
Other than that, remove the old heatsink first by slightly twisting back and forth to break the bond of any dried thermal compound. Remove heatsink, lift locking arm, lift old cpu out, replace with new one, double check for correct orientation. Be careful, work slowly not to damage or bend any cpu pins. Use the right amount of new thermal paste, and if reinstalling the same heatsink, be sure to clean all the old thermal paste off thoughly before reinstalling. Its pretty simple and straight forward procedure, just do it carefully.