As mentioned before with any ICAO licence and yours is already a CPL you can start your EASA theory.
Which path you pick afterwards is up to you. Rudestuff always post good tips for ICAO FAA holders, dig more information about it in Pprune.
CAAwise, a lot of pilots pick AustroComtrol for being efficient.
In regards to PPLconversion it should be simpler than 4 subjects, you can get more info here
CONVERT TO EASA PPL