My Rockbox installed OK but then locked up till the battery died.  Sould I uninstall?  Why do I want rockbox?

It would be helpful if you noted which player you have. But generally, if the player freezes, you can reset it by pressing (or sliding, depending on the model) the power switch for 20-30 seconds, Rockbox or not. Finally, if you don’t even know why you would want Rockbox, you probably don’t need it.