If you have SimPE (but your going to need some patience if you have Bon Voyage, it still has not been updated for it, but if you have Celebrations or lower, this method will work wonderfully), just go to the tools tab, then click neighborhood browser, then click the neighborhood who's sims last name you want changed is in.
Then wait for it to load, then click the tools tab again, and click sim browser, wait for THAT to load and then scroll down or up until you see your sim (it's sorted by first name) double click him or her, and then a "window" per se should open in the bottom of SimPE, there will be a whole bunch of sim info, BE VERY CAREFUL WHEN TAMPERING WITH THIS STUFF! THIS COULD DESTROY A SIM AS YOU KNOW IT!
Look for a box that has that Sim's picture in it, then to the right of it will be two boxes, one for the first name and one for the last name, highlight the last name and then type in the new one you want. Then press commit, best press it twice just to make sure it's saved, then go play your newly named sim! Note: if the sim's last name your changing is in a family, repeat this process for every sim in the family, so each one has the same last name.)
Hope this helps! (You can download SimPE
here )
