Fuel pump and fuel gauge sensor/sender are together in the fuel tank (accessible under the rear seat). This means that your fuel pump renewal and fuel gauge "all over the place" are quite likely linked. Probably worth gaining access and checking the connector is on OK and maybe take the unit out for inspection.
As for the "rail", this is applicable only to engines with Multi-Point Injection (MPI). It is a tube laying across the top rear of the engine that distributes pressurised fuel to the four injectors. If you remove the air cleaner assembly, you'll see a pipe entering the rail at the right hand end (if you are standing in front of the car). At the left hand end is a valve with a dust cover. The valve is similar to the ones on tyres, i.e. if you press down the pin in the middle, it releases the pressure.
CAUTION: Pressurised fuel is dangerous for two obvious reasons; it's under pressure and it's fuel. If you want to try releasing it (to satisfy your self that it was under pressure), cover with rag to avoid the spray and do it when the engine is cold (you don't want to go spilling petrol on hot parts, do you!). When you turn the ignition on you hear a noise from behind you - that is the pump pressurising the system.
If it's Single-Point Injection (SPI), you don't have a rail.
There is also a fuel cut-off switch that works on the inertia principle and should only cut off in a crash. If you suspect that, it should be on the floor near the passenger side sill. It's accessibleto reset it by pressing down.
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