From your first description, it sounds like R-N-D-2, but it doesn't matter really. The point is that you now know the primary problem is in the transmission. The issue is either in the shift spool or the parking pawl linkage. If you are the type that can do an oil change, it is not a big deal to drop the pan and take a look, and is the same procedure as a fluid and filter change. While you are in there, take a look at the linkage going into the transmission and just inside, for how and why it is binding. When you drop the pan, you can see about half of the internal linkage, and it may have simply popped a clip off the linkage, where the fix is 15¢ and 2 minutes to replace it. If the linkage is binding at the rear, you would have to remove the extension housing, taking about another 30 minutes and a gasket to do.
You may want to consider doing the fluid and filter change so you can check yourself, as some transmission shops and mechanics will charge you a lot for that 15¢ clip, if they don't also charge you for a rebuild you probably don't need.
If that's not it, the problem may still be obvious and you can still handle it yourself if you can see the problem. If you drop the pan, let us know what you find, and perhaps some photos if you can.