Tank is vented to reduce vacuum when fuel is pumped out. No pressure in tank. Vents usually open to atmosphere, but some picky government boondoglers (think Kalifornicators) with delusions of intelligence require a filter system. Vent is through a carbon filter that absorbs fuel vapors, which are then drawn out by engine vacuum while running, so carbon never needs replacing. That's pretty much how the rest of the world deals with fuel vapors, but tanks are generally not sealed and NEVER pressurized due to fire/explosion hazards.
Anywho, you can drill the lock itself, pick out the pieces, small needle nose and/or ignition pliers let you pull out lots of pieces. Keep working at it until you free the lock mechanism and no damage to any important part.
From a locksmith's perspective with an unknown lock, it's a cylinder type, like the key mechanism in a car door. I expect if very careful you can remove the lock and still latch the cap, the mechanisms are hooked together somehow, but still 2 mechanisms with different purposes. If you can get the lock out of the way a screwdriver will usually work the latch just fine. I only have experience with a few hundred other brands of locks so don't know for sure about the RX3 gas cap. Mine works fine. Let us know what you find out.
CSC has
replacement gas caps.
RX3 runs fine with gas cap not sealed. Water gets in, fuel gets out.