Will any of the patches I downloaded interfere with the expansion?
There shouldn't be any problems with this but it doesn't hurt to make a backup to be safe.
Because I've come across a lot of very strange and just plain wrong directions on how to backup your Sims 3 game I'll try to make it clear:
I'm thinking I should save a copy of my game just in case
It is
not possible to do that, games or programs installed on your computer can't be copied. That's okay because you don't need it; the game disk
is your backup. If something goes completely wrong you will need to uninstall the game and reinstall from the disk.
So: DO NOT copy anything in your Program Files folder. Copies of those files are unusable anyway.
What you DO need to copy is located in your
Documents/Electronic Arts/The Sims 3 folder. You will want the Saves, the Downloads if you have any, maybe Custom Music if you use that.
The simplest thing to do is to copy the entire The Sims 3 folder. Right-click the folder and choose Copy. Then go where you want to place the copy, like the Desktop or a USB flash drive. Right-click and choose Paste.
Then if something should go wrong after installing WA or a patch you can get the saved games from the copied folder and place them back in the Documents/Electronic Arts/The Sims 3 folder and they should be in your game again.