Sadly, I program in Java and I my sample I would give you is for a MapServer, BUT....
It is really very easy.
You can probably translate this to .NET, I have faith in you.
Create a CenterAndScale object. Use the method to center that accepts a point. Assign it your GPS point.
Set the map extent to the CenterAndScale extent.
Refresh... .and there is your blip.
You have to refresh your map, the other layers have to draw, even when you pan/zoom.
Jeff Matson already pointed this out. You can do things like partial refresh, or set map cache for your layers, or you can dissolved your data so that it draws really fast.
You mention that you are getting a GPS point two times per second. That is really fast, why so fast?
What you could do is use a timer to refresh your map every 5 or 10 seconds, and let the GPS tracker still plot away with the graphics. If your map display shows enough area for a 2 or 3 mile range, I don't think your drivers will be able to drive faster than that distance in 5 or 10 seconds, but I don't know them personally.