Someone broke into my wordpress blog

I need some help, please.

Someone broke into a wordpress blog. I run a script that puts shareasale
items up on that site.

When I look at my stats I have 3397 error codes. This is what alerted me to this site
having a problem.

So I took a look at one of the recent entries and found that I hit a loading page (which I did not put up). When I look at source code, someone has put up google analytics. Then when it goes on past that page, it hits the affiliated site, but shows a 404 page.

I am new at using wordpress, so I used the admin log in page as it came. Should I change that and how? I have a fairly complicated password, but I guess it was not good enough.

I am quite upset, as this is the second problem with someone intercepting my sales on this and another site in the last couple weeks. The other one was a redirect, with cookie stuffing, but they had not put up google analytics. I will have to check my other sites.

Hmmm, maybe I have a keylogger problem, but I run 2 spyware programs and nothing comes up.

Any help would be appreciated. Also tell me how I can get ahold of Google to turn this in?
I will check back in an hour or so.

Thanks.
Jeannie