Hey Scott -
Wondering if you changed out that solenoid, and did it help? There's a possible explanation for the dealer's high estimate (other than them being shady). Make sure it is the actual solenoid that is fried, not an electric fault somewhere else in the system.
I just finished diagnosing my shift-interlock problem with the factory service manual. I am pretty sure the solenoid itself is OK, and at the end of the decision tree the manual recommended 'REPLACE GEARSHIFT LEVER' - i assume it thinks the fault is somewhere in the wiring that is integral with the gearshift lever. It's possible your dealer came to the same conclusion, and that your solenoid may not be the culprit. You may want to make sure before you spring $80 for a new one.
FWIW
