It looks fixable.
For one, you can get a new complete handle repop from many aftermarket places. Sure beats trying to piece together a GM unit. EVERYTHING was sold separately for those things. All that adds up.
But you will also need what they call an "extension", which can be bought aftermarket as well. It screws down into the center detent release rod. A spring on the bottom of the shifter holds all that up. It's probably missing now because there's no way to release the detent.
Even the shifters now are repopped, I think.
Bottom line, don't let that stop you if you want to buy the car. It's very fixable. But I'd use that as a negotiating point. That's at least $100 to fix that unless you go used parts.