Jim,
Kelly Blue Book states for an 2001 LS V8 sport with 35,000 miles is:
Retail = $20,000
Private Sell = $17,000
Trade In = $14,000
What helps is the low mileage on the car. I'd say depending on the market you could probably get around $17,000-$18,000 on it. If I were to ever sell mine that would be range I'd sell mine for.