Well, that's kind of a tough call. It could be something simple like a leaking inake gasket. Or could be something like a cracked block. It shouldn't be that hard to diagnose, though. And shouldn't cost anything close to $1,000, either.
How good a mechanic are you? A few simple tests can be done for really cheap, and by almost anyone who can identify a wrench 2 out of 3 times.
1. Go to Autozone, and borrow their compression tester, and cooling system tester. They'll charge you some money, but you get it back when you return the tools.
2. Recharge or replace the battery. Make sure the engine will turn over freely.
3. Remove all the spark plugs, and check the compression in each cylinder. Then squirt about 1/2 oz of motor oil into each cylinder. Spin the motor over a few times, and then check compression in each cylinder again.
4. Check cooling system, and make sure it can hold pressure cold. If it can, start the engine and follow the instructions that come with the tester.
5. If either of the above tests are abnormal, buy a coolant reagent test kit at NAPA, to test for byproducts of combustion.
6. A leak down test would be nice. But that requires some specialized equipment that's not easily borrowed or rented.
Those three simple tests will give you a boatload of information. Then you can make some decisions.
'08 V6 Pony
'65 Monster FFR Roadster