Transmission

I have a 1997 Park Avenue Ultra. 75000 miles. The fluid and filter was changed at 60,000 miles. I use Mobil 1 fluid, which is currently at the proper level. During the last week I noticed a whining sound and slow shift to third gear when the car got hot. Last night after exiting a highway (no problems) when accelerating, the car responded as if in neutral. The car now only moves when the lever is in the 1 or 2 position. Any ideas short of a new transmission would be appreciated.