How unsafe is it to change sims' names?

[kuronue]

Now i am totaly confused what name to alter in Simpe is unsafe?
 I dont understand the surename, lastname, firstname, whatevername thingie.
 Please explain it someone for dummys like me.
 I have altered a Thomas to Aaron in Simpe. If i understand right thats the no no. (made it later with the Lotdebugger)

To alter a Thomas Wood to a Thomas Smith in Simpe is alowed ? Or is it also a bad thing to do.

That's right. Surname = last name = family name.

[Theo]

The OBJD also carries the first name of a sim, and renaming in SimPE will not change this.

I see, that's the value that will appear on error logs, so it's better to rename it as well to avoid confusion.