Short answer is: yes it is possible to extract the ROM from the RIL ( radio Layer).
However, you will need to look at the posts in detail because it is a complex process and it can cause many hours of frustration. Many of us feel that if you are happy with your Radio stack ( meaning it works and does not cause you to loose calls or similar things) you should keep it, as opposed to figeting with a new one and potentialy lobotomizing your unit.
Whatever you do use the SD card method of upgrading and follow those directions closely. Shortcuts will cost you in the long run...