Jake
To be specific about your questions, you need to remove the rubber mat or carpet over the tunnel, take off the black metal 'heater' trunking at the front and the flat black access panel at the rear of the tunnel. I have incuded a photo showing the connection of the hose to the rigid pipe from under the car.
I have a RHD 69F, I assume that all the cars will be similar. When you remove the mats and covers etc the run will be self evident. The hose runs across the top of the tank, down throught the firewall and into the passenger footwell. Inside the footwell it runs around and down the wheelarch, across the front of the footwell, bends again to run through the inside of the tunnel (on the left had side). Exits the back of the tunnel and joins an rigid fuel line. This rigid line terminates in the engine bay where a short length of hose connects it to the fuel pump.
Any transits through sheet metal are protected by rubber grommets. Tabs inside the tunnel and footwell secure the hose.
Remove the mats and covers inside the car.
Take photos and notes of how the hose runs. Have a torch handy.
Loosen any tabs you can find in the tunnel.
Disconnect the hose at the tank and plug both the tank and the hose.
Disconnect the hose under the car and let the fuel in the line drain out into a container.
Plug the ends under the car.
Pull the hose out gently and then run the new hose.
(Thinking aloud, you could try joining the new to the old with a piece of pipe under the car and pulling the new in as you pull the old out. Not sure how this will go.)
Reconnect and check your connections.
As always, make sure the car is well supported when you are working underneath. Make sure you plug all the lines as you disconnect and double check as you connect. You do not want the throttle choke or starter cables rubbing against the fuel hose in any way after the replacement.
Replacement is not difficult, just fiddly. Do not plan on going for a run an hour after you start.
You can see the fuel line exiting the tunnel, curving up to join the rigid line that is a coppery colour. This photo does not show a hose clamp that was added later.
Regards
Joe R