If the mechanic has told you $1800 without even looking at the car, go find another mechanic. To blindly give you that high a number right off the bat without doing some diagnostics is insane. Injectors themselves range from $35 to $60 each depending on where you buy them. O-rings and other injector seals, including holders, would only run another $50 or so. Check this site (Buy Parts) to get prices, but realize the mechanic will mark up the prices if he buys them. I assume he is talking about replacing misc hoses and lines which should not add up to that much.

I just installed them in a 1989 and it was a piece of cake. If you do not replace the holders, just hold them down when pulling out the injectors to prevent dislodging them. I'm not sure the injectors would cause the hesitation you describe. I would have the mechanic do a fuel pressure test. This will determine if the injectors are leaking among other things. Don't forget about the ignition system. Spark plugs may help as well. Might check the vacuum advance line to the ignition module to make sure it is not broke or plugged. Take a look under the hood and air cleaner yourself and look for obvious problems, such as broken vacuum lines, lines that have came off, wiring that is bare, disconnected wires, fuel leaks, and other stuff. These cars have a lot of junk under the hood that can deteriorate with age and heat, and can cause problems. Does it act like it is missing or does it simply not want to go like lack of fuel? Does it act up when hot, cold, or both? Being as specific as possible about the problem will help in diagnosis.

I know what you're saying about always something with these cars. Been fighting a hot start problem, and I think I pretty much have it whipped after many $$$. Nothing is cheap on these models.