Fords are not exactly Hyundai but to relieve fuel pressure on my
Accent you unplug the electrical connector to the fuel pump, start the
engine and when the engine stalls the pressure will have been
relieved.
I dare say that if you do the job in the morning before the fuel heats
up, you'll get away without removing the fuel cap. The reason for
removing the cap would be because of fuel expanding as it heats up.

For a very plain website try
http://ii.net/~farmerjim/

There's probably a schrader valve on the fuel rail which you can use to
relieve the pressure.

I've never bothered with the pressure relief. Start with a completely
cooled off car and take the fittings apart slowly. The ford fuel
filters usually have a plastic clip that needs to be pulled out
perpindicular to the line, and then the lines can be pulled off the
filter. Pull slowly, expect a small amount of fuel to leak out as the
residiual pressure bleeds off and then pull both lines and change the
filter. You'll wind up with whatever fuel is IN the filter all over the
ground irregardless of whether you bleed off the pressure or not, so be
prepared for that.

I would say you do not need to remove the gas cap but it can't hurt to
loosen it.

Chris