FANS (Future Air Navigation System):
Uses the airplane's ACARS system to transmit/receive _data_ relating to flight planning (rather than voice transmission/reception). Data is requested or received via the Flight Management Computer CDU on the flight deck... which is hooked up to the ACARS system (which is hooked up to your Centre VHF or to your Satcom systems). If you have Satcom, this is (or rather, should be) much more efficient than HF voice tx/rx over medium/long distances. VHF is used for short distance data transmissions.
You can request flightplans using the FMC (CDU) and even upload them directly into the FMC. You can upload modifications to your flighplan (en-route) to take advantage of favourable winds. You can fly off the standard Airways (you may need extra accurate navigation systems tho'... such as GPS... and good traffic avoidance systems.... such as TCAS).
ETOPS:
Special regs and rules apply to twin-engine aircraft making long overwater flights(or any flights a long way from suitable airports). Your aircraft may be restricted to flights which ensure that you are not more than a certain flight time away from the nearest suitable airport). E.g. 120 minutes (can be smaller or greater).
Hope this helps.
Rgds.
Q.