yes, you have to unlock the phone first. Instructions here.
http://forum.ppcgeeks.com/showthread.php?t=42503
I recommend Mighty's Rom. His is most popular. Here's a link
http://forum.ppcgeeks.com/showthread.php?t=52695
But everyone has different taste. You can check all the different roms out in the upgrade sub-section here
http://forum.ppcgeeks.com/forumdisplay.php?f=68
Let me know if you need any help with it.