fm's new-liquidcrystal library

I am relatively new to Arduino.

I have a new I2C 20x4 liquid crystal display. I am looking for the best library to use to drive it. I understand that fm's library:

Is a good one. My question is that the instructions indicate I need to remove the original liquidcrystal library so they do not interfere with each other. Does this mean that all my programs will need to be re-written to use the new code? Or is the library from fm backwards compatible? I have another project that I tweak from time to time that uses the old library.

Thanks in advance.

The library is backward compatible.

To use the other types of interfaces (I2C, etc) you invoke a slightly different class.