The fuel pump can be accessed through a panel under the rear seat (as you suspected) - removal is pretty simple - disconnect the fuel line (make sure you de-pressurize the system first), remove the nuts holding it in place, then pull it out.

 

Check out member wrXratd's fuel pump install. He has a wagon but the sedan is similar.

--
0==WW==0
"…axles of evil…" - george w. bush

 

It is accessed BEHIND the rear seat. The sedan has an access panel just behind the rear seat, passengers side.
Taking the rear seat out to remove and replace the fuel pump is the easiest way to do it, IMHO.

 

I did it without removing the seat, only because I couldn't quickly figure out how to remove the seat!

 

you should also use a offset screwdriver to remove the cover, it makes it a lot easier. i also didnt remove the seat.

 

Yes please depressurize the system. My friend found out the hard way in his Civic SI and fuel sprayed everywhere!! LOL

 

where do you depressurize the fuel system...

 

Unscrew the gas cap before you start the job.

 

From experience, starting the car and letting it stall after you unplug the fuel pump (and unscrewing the gascap) is NOT enough to depressurize the system. Trust me.

I don't know the correct way to REALLY do it. I've just gotten good at soaking up a jet of fuel!