Doing that kind of upgrade on a laptop is not easy business. First, it wont be easy to find a GPU for the laptop on the market (but not impossible. Second, if you do find one you must be sure it will fit inside the laptop housing with all covers on. Third, if your laptop only has a VGA port, you will have to cut a new hole for the HDMI port so you can have access to it. Not to mention powering the GPU, will your current PSU cover the power needs of the new setup?
Your best bet would be something like this:http://www.amazon.com/Unknown-HDMI-VGACONVERTER-Audio-HDMI-Converter/dp/B0015YWV1G