Some of it's easy, some of it's a pain in the butt.
Here's a version without the curr/max and % text on the bars. Just drop it in the MookUI folder. If you compare it to the old one you can see that it's just some Text tags removed.
If you want the % back in... well, take the first step and copy it back in. Don't be afraid to start poking around and messing with stuff, that's how I got started, and you can always run the patcher and revert back to the default UI if you break anything.
Go on, it's empowering.
(I'm probably going to take a break from the modding for a while, but Ellyana is working on some big gauges here:
http://www.eq2interface.com/forums/showthread.php?t=419 )