Jon, it's not quite as simple as pulling the old one out and pulling the new one in. Here's the steps I take:
Remove the center console.
Remove the center tunnel carpet, center arm rest and remove the access panel at the rear of the center tunnel.
The speedo cable is normally held in place with several of the wire tabs that hold the main wiring harness in the center tunnel and on the front firewall, loosen these wire tabs.
Pull the cable out from the firewall in the engine compartment, being careful that the cable doesn't get hung up in the center tunnel section.
Disconnect from the tranny and pull cable from the engine bar.
Install the new one.
Tape the 'ring' on the speedo end of the cable with electrical tape.
Feed the new cable in from the engine compartment so that it just clears the firewall.
Go into the interior and pull the cable from the access panel at the rear of the center tunnel.
Feed it up into the area of a center tunnel where the main wiring harness lays.
Feed the cable underneath the cross bar, where the front of the seats attach.
Pull the cable long enough to attach to the speedo.
Remove the tape, but remember to keep the ring close to the end of the cable, as it will slid when you try to attach it at the speedo.
To attach to the speedo, I have the instrument cluster pull out so that the bottom section is against the steering column and the top pivoted towards yourself.
Once I can see the cable, reach up underneath the dash, grap the cable, with the ring, then push the instrument cluster back in place, while trying to feel where the cable and speedo connect.
Carefully screw the ring onto the speedo.
Go back undereath the car and feed the tranny end of the cable through the engine bar.
Attach cable to the tranny.
Test the speedo. If it's working correctly, tighten the wire tabs, replace the access panel, carpet, center arm rest, center console, instrument cluster.
Here's a shot of the center tunnel where the main wires and speedo cable lay.
BTW, if you know anyone that has small hands, they should be able to help with the attachment of the cable to the speedo. Also having a second person helps alot.
Good luck...
-- Rob