Depends on the age of your BP-25. If the RCA plugs barely stick out through the back of the unit, it is the older one and they have to do some board replacement.
If you have the long RCA jacks, then your board is up to date and all they need is the new outboard power-supply. No modifications required. I think that they made the change about late 98 or early 99. Mine is a '99 model and no mods were required save for the new power-supply. (Which makes a HUGH difference.)
May I recommend that you wait until they make their digital unit a stand-alone one? Things will sound much better if you have seperate power-supplies, and boxes, for the digital and analog ciruits.
I bought my phono-section as a stand-alone, and even though it is the exact same ciruit as the phono-stage in the BP-25, it sounds like a much more expensive phono-stage. Noise and power-supply isolation mean a lot.