Remote access from PC to Mac

I for one have only done the reverse, but I am sure you can get software that does what you are looking for in the Remote Desktop or VNC realm. The hardest problem is your IP address changes at the whim of your internet service provider. Dyndns can give your Mac a static domain name which will overcome it.
The website http://www.macwindows.com reviews many such tools. Your other problem is many offices don't let you remote out of them without a VPN setup. I have used harris VPN, which works great to get into my work. Talk with your work IT about it.

On the Mac, go to System Preferences > Sharing > Screen Sharing. Then click the "Computer Settings..." button. Hidden in there is an option to turn on the standard VNC server and give it a VNC password.

Have you looked into tools such as LogMeIn, or Hamachi? I have used the free LogMeIn to remotely connect to my mom's PC to fix it for her. Granted, that is controlling a Windows PC from a Mac, but I have also let a friend remotely control my MacBook Pro from his Windows PC just so that he could see how a certain app looked in my environment. I like this solution enough that I have also purchased the "LogMeIn Ignition" app for my iPhone allowing me to remotely control any of the computers in my account from my iPhone. Great for emergencies.