update the firmware on your PS3, the latest version of Java should now be supported.
If you choose to go with ubuntu, you'll need a keyboard and a mouse, and it'll be an adjustment to get used to using it on your PS3 (strong learning curve if you've never used a linux OS)
ubuntu is an operating system, kind of like windows. Personally, I haven't used it (more of a thing of I know windows, and I don't feel like having to learn a new operating system just yet).
IF you choose to go with ubuntu, you'll have to run whatever you're trying to do through it, and not the PS3's OS. But, whatever you are trying to do, should work with the PS3's browser. If it's not working, then you can try ubuntu, but have fun learning it ... I hear it is the easiest of the Linux OS's to learn though...