First of all, I don't know where you live, but a 95 Cutlass is maybe a 1500.00 trade in. KBB is tits-on-a-boar hog-worthless, unless you're the one selling the car.
Go Here and use the Black Book to figure out what the dealer might have in the car. Rough book is generally what you get on trade, so figure that plus maybe 400 bucks to get it ready for sale, unless they tell you they put brakes, tires,(you said they did, actually). So add whatever the tires cost to it.
That's probably pretty close to what they have in the car, unless they practically stole it at auction or something.
Now, average dealer profit on used cars is 1500.00. If they will come lower than that, then more power to you. But that crap about dealers only needing to make 400.00 on a car sale is just that, crap. If that's all they made on every sale, they wouldn't be in business for long, especially new car dealerships.
If you buy a 10,000.00 car for 10,400.00, that's what, a 4% profit for the dealer? That's what a lot of people will tell you is fair. Then those same people will ride with you in your new car to the mall and both of you pay 50.00 for a polo shirt that cost the store there 8.00 and think that's ok.
So if a dealer has 10k in a car and you can get it for 11,500.00, that's only 15% mark up. Not a bad deal. Of course, if you can get a better one, go for it. Use the link I gave you to figure out what you think is a fair price (average retail is pretty fair), and just tell them that's how much you'll pay, and stick to it. The best way to "check their temperature" is to get up and start to leave if they balk at your offer. If they start kissing your butt trying to get you to stay, you're probably going to get your price.
Sure, car dealers have a well-deserved reputation for being crooked that has been built up over many years. But that doesn't change the fact that they do need to turn a profit, so they'll be there next time you need a car. So just stick to the black book values, especially for trades, and you'll be playing in the same ball park as they are.