You can also skip Ambrosia or the Book of Life and make a Sim who's died back into a normal Sim by removing this ghost trait once they've been added back to your family. If it does not, you can try other options: testingcheats 1, testingcheats true, and testingcheats yes all work to enable the cheats.To enable Testing Cheats, open the console with Left CTRL Shift C (press/hold in that order) or by pressing all four shoulder buttons on console and type testingcheats on. You must do this every time you load an area until a bug is fixed.
This will let you change the gender, traits, everything, and is much more powerful than the scaled down version you get without typing this cheat.
Testingcheats on should be enabled, as some cheats will not work without it. Money X - Type Money 50000 or 1000000, whatever you like, and your family will have that amount exactly.
This can be used to subtract funds, because it sets the money to whatever amount you specify.
You are also able to completely redesign a Sim by shift-clicking them and selecting Modify in CAS.
This takes you to Create-A-Sim where you can make the Sim look however you want, but not change their gender or traits.