Crankshaft Position Sensor
 

So my Check engine light went on, had the codes read and the Crankshaft position sensor is out, there's a misfire in cylinder 8, and there may be a leak in the EVAP system or the catalytic converter is out. I've already changed out the plugs and coil, next I am going to replace the crankshaft sensor, can anyone tell me where the sensor is located? I've heard it is on the transmission's bellhousing but I want to make sure before I start. After that I plan on replacing the fuel injector, we'll see if that takes care of the problem. I'd like to try this out before I buy a new cat converter, theyr'e pricey!

It depends on the code, there is an RPM sensor and a crank position sensor. One is on the engine while the other is on the transmission bell housing.
However when these go bad (shorted or broken signal) the engine won't start, if yours is running and has a code i would pull the connector and check for corrosion on the pins or check the sensor for visible damage/checking the gap.
The connectors are next to the O2 sensor connectors located on the firewall behind the engine, crank sensors have black connectors.

The codes comming up are: P0442, P0321, P0308. The engine is running but hesitates a little. I changed cylinder 8's coil pack and saw some oil in the back of the engine, specifically where the connector is; I wouldn't be surprised if oil got into the crankshaft position sensor and is making it act up. Next on my list is to change my valve cover gaskets and replace injector #8 since I"ll ahve the injectors off already.

I would not assume an injector problem until you address the crank sensor. Why would you have the injectors out? ...not needed to change valve cover gasket.
What year car? If 99 or before, might want to check ignition output stages...switch left for right to see if misfire moves to the other side.

I will try that see if the misfire changes side. Audi told me they'd have to take out the injectors for the valve cover gasket chance, great to see a dealer helping someone out right :) I looked at the sensor plug yesterday, it looks fine. while I was back there I found it interesting that I was able to remove the Oxygen sensor with my hand so I tightened it up a bit.

So I replaced the crankshaft position sensor and it runs better. Swapped the coil from cylinder 8 to cylinder 7 and it made the engine a little shaky; I'm going to replace that coil I think it's gone bad.

Its more likely one the ICM's (ignition output stage) has gone bad rather than the coils. I think silverd2 wanted you to swap the connectors on the two to see if the misfire moved to the other bank.

Yep, if you have a 99 or before..you never said...very different from 2000 and up.
If 99 or before, look at this: http://forums.quattroworld.com/a8/msgs/6383.phtml

I have a 1998 A8, I'm going to try the ICM there a way to test it? besides swapping the coils? I found the part on e-bay, it runs about $60 for an aftermarket piece.

Yes..a Bentley manual and the special Vag electronic testing tool they specify.
Swapping power output stages sides from one engine bank to the other is a sure-fire test. If the misfires switch engine sides, it's the P.O.S. box.
...or you could take a $60 ebay chance(?)