How to Update Arduino Uno Firmware

After having problems with Serial on Ubuntu (fixed it with windows by uploading blink sketch) someone gave me a link to this topic But I'm scared of updating the firmware in case I fry the board. Is there a step by step tutorial of how to do it properly and which files to download? Thanks in advance, ell

Sorry, sorry, sorry and sorry for being such a pain on these forums but I have fixed my problem! Sorry again!

Please post how you solved it as others who are searching for the same problem find your thread and could use solution.