2003 Tundra tranny linkage freezing up

Any thoughts on tranny linkage freezing up reasons and fix? Is it common for them to be very difficult to shift with corrosion? It came from MA and had been sitting for quite a few months prior to me buying it. It just had the frame replacement done and stealership said it was the 2nd worst one they've seen. Can shift in and out of gear from lever connected to tranny with channel locks but thats very stiff and not easy either. What are the odds that it could be internal to tranny? Is there an effective way to free it up without taking transmission apart? I don't mind getting the parts and cable for the column but am hoping trans isn't in need of a swap. Thanks!

 

Is this that infamous kick down cable the SC guys are talking about, related to the transmission. It's a steel throttle cable?