I'm not too sure about the voice, but I can tell you how to install Custom XMB's.
HOW TO INSTALL CUSTOM FIRMWARE
*USE AT OWN RISK, THERE IS A CHNACE OF BRICKING YOUR PSP AND LEAVING IT
UNUSABLE*
Go into Recovery Mode>Advanced Configuration and then Toggle USB
(Flash0). Now plug the USB cable in and your Flash0 will appear as a
removable drive. Be sure to backup ALL of those files to somewhere safe.
Follow these instructions perfectly or you could brick your PSP.
There will be a topmenu.rco file (this part only applies to 3.40OE-A)
you will need to convert it. Use a topmenu converter.
Here is one thanks to Xyster:
http://www.arkosoft.it/pspdragon/wp-content/uploads/2007/04/upgrade-topmenu.zip
Now replace the old topmenu.rco in the downloaded custom theme with your
new one. Copy all your files from the custom theme into X:/vsh/resource,
overwriting previous files.
If you run out of flash space,free up space with the instructions below
and and copy the custom theme files over again.
1. Disable your internet connection.
2. Connect psp to pc and enter recovery.
3. Go into Advanced -> Toggle flash0.
**You should now see your psp flash0 as a removable drive on your
computer. Be VERY careful, one rogue click, one wrong file deleted and
you have a brick.
4. Carefully make a full backup of flash0 from your psp to your pc. Just
copy and paste the whole thing.
5. Now, from the PC BACKUP of your flash0, go into the font folder and
copy file ltn0.pgf to your desktop. Now rename ltn0.pgf to jpn0.pgf. Now
go back to the font folder on the PC BACKUP of flash0 and copu ltn0.pgf
to your desktop again. This time rename it to gb3s1518.bwfon
6. Copy these two files from your desktop to the flash0:\font\ folder of
your psp. If it asks you to overwrite files say yes.
7. Toggle flash0 again in recovery menu and reboot psp.
After you have done all this, disconnect your PSP and exit recovery. Now
go to Settings>Themes and choose "Original" now you have a Custom XMB.