OSC is a protocol which allows devices and/or software to exchange messages each other like you can do with MIDI. This is not the solution to everything.
Regarding the way you could display sheets music in GP, you could perhaps have a look here:
You could also simply use an iPad as an additionnal display to keep things « KISS ». I personally uses an iPad with the NewZik App which has probably the nicest GUI of the industry (and many other nice features), but it misses the Program Change option to sync with GP songs. Another very good alternative is MobileSheets which has it.