Kill someone if "this crap" doesn't get fixed? "This crap" is your computer and your install. There's a lot of things you can do before getting angry.
*
Have you tried running repair.exe in the WoW folder? (And for the love of god - Don't say "yes" if you haven't done it. This fixes so many installation/updating problems it's not even funny.)
* Is your disk full?
* Have you tried reinstalling Wrath from scratch and started updating again? (they can't "fix the bits" from their end - if there's a problem running the updater, this is what they're going to tell you to do.)
* Have you run a disk scan?
Re-installing and updating is your best bet at this time (after running repair.exe and seeing it that fixes it). Hope you're not near your traffic cap.
Note: If repair.exe is missing, you can get it here:
http://ftp.blizzard.com/pub/WoW/other/Repair.zip
You shouldn't have to "set the installer" to install anywhere in particular - it should install to the current folder WoW is installed in.
Rather than trying to run a patch update separately, run
launcher.exe in the WoW folder and let it update from there.