boot loader

Hi, I'm new in this forum, and I would like to apologize if this is not the right place to ask the following.
I have Arduino 2009 but I've recently burned the MCU. I'm about to replace the MCU with a new one. My question is, will I have any problem downloading my software codes into the new MCU using the Arduino 0018 programming software? Is there anything I have to know about boot loader?
Thanks to everybody would help me.

Ciao