I'm not entirely sure what you mean by it won't go into gear. You mean that you try to push the buttons and they won't go in? If so, then I'd think there's a problem with a) the pushbutton mechanism itself, b) the pushbutton cable, c) something inside the trans or d) the park mechanism isn't releasing. Which reminds me: did you pull the park lever out of park before trying to put it in gear? If not, there's your problem, as it will not go in gear while in park. If you did try to pull the park lever and it won't move, then likely the park cable is frozen, or some problem with the park mechanism. You will need to remove the cover to inspect the park internals, and also disconnect the cable to see if it moves. (I have a NOS park cable in my parts stash that is frozen, so it does happen.) If "park" isn't the problem, IMHO the easiest thing to do is pull the pan and look at things. Number one, I've always found it easier to adjust the cable with the pan off. Also easier to disconnect the cable, too, as there is a clip deal that needs to be moved out of the way to release the cable (after you've removed the bolt from the adjusting wheel, of course), and that is much easier to do with the pan off than trying to poke a small screwdriver through an opening like the manual says you can do with the pan on. Once you remove the cable, then you can figure out if it moves OK when you push buttons. If so, the problem is in the trans. If not, it's in either the cable or the pushbutton mechanism itself.
