Speedo help

How I do it. When I'm removing a panel, The speedometer cable has a little sheet metal strap under the drivers seat area to hold it in a slow curve there. Set the cable out of that strap.
Next I find the speedo cable comming through the firewall, pulling there and pushing towrd the dash should push the inst' panel out of the dash. Just a few inches is ample cable to put it back together again. Just remember to push the cable back out of the firewall drawing the panel into the dash rather than have that cable put excessive force on the instrument.
Where you are now... Disconnect the neg' battery cable. Take the one phillips oval head screw out of the fuse box. Gently lift the box out of its bracket and move it away and down so it rests behind that bracket. Pull the headlight switch full on, push the stem release button on that switch body and remove the knob/stem. Remove the switch bezel nut and push the switch in and under the dash. These simple moves should give you plenty of room for your arm and your seeing the cable connection.