Qns on custom rom

[Guest Sillypore]

i'm new to Omnia custom roms, so i need some advise & answer before i start flash mine.

1 - do have i to mod/change the reg if i'm going from a official to custom rom?

2 - do i still need to install PortSpilter or GPSgate in order for gps s/w to work?

3 - (this sound abit silly) does flashing to custom format my 16G?

thanks for all valuable advise & info.