I have yet to install linux on my ps3 so I cannot help you much with troubleshooting. I guess you could load it on your computer so you can see where the buttons and stuff are. Once you know that then you could just use the TAB button while on the pages to scroll through the options and use the SPACEBAR to change the options.
Have you actually installed Ubuntu?
If you have, just change the screen resolution in the system tab.
Honestly, I'd recommend installing puppy linux. Not as powerful as ubuntu, but its almost like comparing XP Pro with XP home.