If you want a free solution I recommend VNC.
This is what you have to do:
1. Install a VNC Server on the computer at work.
2. Configure the VNC Server (Password, etc...)
2. Select the listening Port (Usually TCP 5900 + screen number).
3. Install a VNC Client on you computer at home.
4. Wait for the IT guy to do his work (See below)!
5. Start VNC and enter the IP adress or Domain and password, then connect.
This is what the IT guy have to do:
1. Open the ports you specify above in the firewall (TCP 5900 - 5904 ?).
2. Forward these ports to the internal IP adress for your work computer.
3. Give you the external IP Adress or Domain name you should connect to.
4. Stay put if something does not work!
The only downside with VNC is that it does not use any encryption.
Good luck!
