yes, if you turn his battery into a pandora it will work on your slim. It wont fit in very neatly, but it should work. Once you have it all done you can start his psp up with the charger and no battery in, then pop the battery back in and revert it to normal.
If your dad's psp is already on cfw... then use Pandora's Ultimate Magic Stick to make a pandora battery and mms.... just insert the PUMS file into the ms/psp/game.... and run it.. see if that work
I get a 80020148 This game could not be started error
And jackspiver you mean U.P.M.S i know about that, i tried it on my cousins slim, it got bricked. but if theres a newer version out there link would help
PANDORA CREATOR error 80020148
Check this thread out^^
Most likely you'r dad doesnt have the 1.50 kernel on his psp. Which is weird because cfw lets you choose it even though its not there. I would just grab the 3.xx eboot and try it out.