undefined function to get header

I have completely screwed up my family’s blog site (www.lettersfromtheloft.com). My brother did me a favor by setting up wordpress on his hosting account, and then he left me to administer it (since it was my blog in the first place). The host appears to have a malware problem, though, as I keep getting redirected to a malware warning for a certain IP address in the Netherlands. Oy.

In my attempt to find & fix the redirect, I’ve messed up the wp file structure.

I think I accidentally replaced the index.php file under wp-admin with an index file from a different folder. So I found the correct wp-admin folder on my computer, and I tried to drag that over to replace the incorrect one. But that didn’t make the “undefined function to get header” message go away when I try to view my home page.

Then I dragged the entire wp-admin folder over (in case my brother had used a different version of wp than the one I have on my computer – even though they were probably downloaded on the same day). It took a LONG time for FileZilla to finish this process. (edited – I see now that it didn’t REPLACE wp-admin, but added a new subfolder called wp-admin in the existing wp-admin folder. What do I do now?)

It’s still not working. I’m about to start beating my head against a wall. I’m not a web developer by any means, and I’m having trouble detecting the problems. My brother is too busy to deal with this.

Please help. 🙁