Yes, a new PC user bulks up the security and protection of their new PC by taking off Internet Explorer and using Firefox or Chrome, because Firefox and Chrome have fewer quirks and problems. Internet Explorer is not only less secure, but it also doesn't display pages as cleanly as other browsers do.
Many of the different viruses and spyware is designed around Internet Explorer since it remains the most populated web browser in the world and those using Internet Explorer are often less technology adapt then those who take the initiative to install a browser like Firefox or Chrome, you will only be benefited by using one of those browsers over Internet Explorer.
No, you can still get just as many thing on your computer that can hurt you from using chrome and firefox as you can from internet explorer. It is not what you use, it is the websites that you go to and the things that you download from the web.
A new PC user would lack the knowledge between the differences in security of different browser types. A new PC user would likely choose a browser based on the user friendly features and ease of online searching. Overtime, a new PC user may begin to distinguish the differences of security between browsers and may choose a different browser than Internet Explorer as their primary browser, but this would be after a while of online browser use.
I do not believe security on a PC can be improved simply by removing Internet Explorer and installing a different free browser such as Firefox or Chrome. I have preferred Chrome on my PC, but it didn't stop me from downloading a virus that eventually led to me wiping my PC.