Not Sure if I Need Help or Not. Please Help!

I'm not sure if Yahoo was trying to sell me something I don't need, or if there is really something wrong with our home network. Please read what I do know and give me your advice. Also, if I do need help, tell me where on MG I should post (software, hardware, etc.). Thanks in advance!

Scenario:
I use Gmail for my "real" email and have a Yahoo account for use when I have to give an email and know I'm going to get junk mail. I log in to my Yahoo account a few times a year to delete what's in the InBox and that's literally all I use it for. I do not send emails from Yahoo. Ever.

Events as they happened today:
I get a Gmail saying Yahoo is requesting I change my password "due to recent security incidents online"

I log into Yahoo, change my password, and go to delete the 1,100 messages in my Inbox when I notice there are a bunch of messages from MAILER-DAEMON@yahoo.com at 11:40am. I open one and it says: Sorry, we were unable to deliver your message to the following address. [insert email for someone I've never heard of] Error code 475: Suspicious activity was detected on your account. Each one of these emails has a different 'sent to' email listed.

Concerned, I call Yahoo support. They spend about 30 min on the phone with me. They have me agree to screen sharing and I give them control. They check my home network settings and find a list of 4,500 errors. They go to the cmd prompt and run something that looks like a tree (cmd.exe?). It takes forever. Toward the end, the white lines and letters turn red. Yahoo tells me they are concerned. Another guy from Yahoo comes on the line and checks something else. He shows me a list of established connections to my home network. Some of them say "foreign" and he tells me I have 11 established connections being used from other countries. Then he starts trying to sell me some service that will fix all this and protect my personal identity.

I get a phone call from the CFO at the company I work for. At 7:40am, he received an email that appears to be from me and my work email (not Yahoo), directing him to wire $42,000 to an account. He tries to reply to the email and discovers it's a Yahoo email, not my work email. He calls me and discovers I never sent him the email. No money was transferred. The most tech savvy person we have at work (we don't have an IT guy) suggests I exchange my modem/router for a new one from my internet provider.

What do I do? Where do I start?

 

Thank you! I feel like such a fool. I Googled Yahoo customer support and got the 800 number from there. Now that I've searched the phone number, I see it's not for Yahoo! it's another company altogether. Called Yahoo Support Number, they are a third party not affiliated with Yahoo!

The good news is I called my ISP and they do not show any foreign access for my home network. They did tell me that Yahoo! has had a suspected security breach, as they've gotten lots of calls. I have no idea if that's true or not. To be safe, I have a new IP address and password. I've also run every scan possible (from suggested sites on MG) and my laptop is clean. I had tracking cookies, but that's it.

Now my concern is what info they accessed and what, if anything, they do with it. They are a real company, with real contact info., so I feel okay about that. They just have a shady way of getting customers which makes me uneasy!