Hello,
I'm planning on upgrading to Wrath of the Lich King in the near future.
Although the game itself will be purchased in the upcoming weeks, I intend on upgrading my game files ASAP, so I can just enter the Activation Code, and jump right in.
I have a simple question regarding the update.
After I download WotLK, will I have to fully re-patch my game? (Including the dreaded 4.0.1), or will I simply have to wait for the expansion to install? (I can't compare the upcoming experience to BC, as I installed with the disc, and the files were corrupted- I had to reinstall)
Thanks in advance.

You should have the content already, and you will just need to upgrade. the accoutn with your key.