Tonka Trac,
It's difficult for anyone to say how hard or easy it is for YOU to do anything?? For someone with a lot of engine experience, it may only be a two hour job, while a person with little or no engine experience may take several days and still have problems.
$800 may sound like a lot, but how much are they charging you for the parts and how much of that is labor? Remember, that if you do it, you will still need to buy the parts, so you have to judge whether you are willing to take on this job rather than pay?
I would be curious as to how they determined that your intake was cracked ?? The intakes are plastic and may have a different expansion/contraction rate when the engine heats and cools. That usually effects the gaskets before it will necessarily crack the intake.
The problem I have with many of these dealerships is that if you agree to pay for them to replace the intake is that the intake may not be cracked and may not even need to be replaced, maybe just the gaskets, but they will blindly replace the intake and charge you for it.
I would want more proof that it is actually cracked and they would have to have to show me where the old one was cracked. Even then, they might just wack it with a hammer before they bring it out to show you.
I would feel more confortable if they said that it "Might be" a cracked intake manifold or perhaps a leaking gasket. That would indicate that they will examine the manifold when it is removed and perhapes pressure test it for leaks and replace it only if they confirm it is leaking and not just a bad gasket.
It may only be a cracked vacuum hose which will give you the same symptoms as a cracked or leaking intake. Either way, there is a test with a small propane torch that will locate where the vacuum leak is fairly accurately. (within an inch or two). If you ST was still under warranty, I can assure you that Ford would not pay them to replace the intake manifold unless tests were done to rule out any other source of a vacuum leak.
Remember that the Dealers operate differently than most other repair shops. The Dealers charge a very high labor rate to discourage you from wanting to pay them for a lot of troubleshooting and diagnosing of problems. They would rather you pay to have the part replaced and they make the profit from the labor and the markup on the parts.
Most other shops charge less than half the labor rate that a Dealer charges and is more likely to diagnose the problem and fix it without replacing unneeded parts. But that is just a generality and does not apply to all Dealer or all independent shops.
...Rich