Fonts are easy to change by renaming the replacement font files to droidsans.ttf and droidsans-bold.ttf. Theming requires decompiling and editing framework-res.apk and SystemUI.apk at minimum. System apps may need to be decompiled and edited as well for consistency.
OMG !!! second try to change font now stuck on bootloop So now how to recover with adb hmmm cwm doesn't seem to work or can't reboot into recovery only got working adb?