Shift lever on an 88 Cadillac Seville moves without resistance but the car won't shift out of Park.

1988 GM Cadillac Seville Elegante - Transmissions & Drivetrain

It appears that the gear shift lever on my Caddy isn't connected to the transmission anymore. The shift lever moves up and down without the usual resistance but the gear doesn't shift out of Park.

I'm assuming that I need a new shifter cable. Is there anything else I should be considering? Is there any additional information, etc. You might suggest? I'd like to try and repair this myself. However, if that's not likely how much should I expect a repair like this to cost? How long should it take? I appreciate any help you can give.