It is fairly easy to install. Take instrument panel out and follow cable through fire wall. It is sometimes attached to tranny or tranny tunnel by some small connector. It will end at the tranny. Both ends screw off fairly easily. Maybe have some PB Blaster for the tranny connection. I replaced one, but I do not remember the cost. Depending on how bad the cable is, you might get away with spraying some silicone down the cable at the instrument panel.
As for being 'flexible', you will need to be able to bend over into the engine bay.