Mods I recomend:
Put Koni sports in it and be done with it. Yess you can go cheeper but this is the one single place I would not. It is by far the best mod/upgrade I ever made to my car. While you are there put Iboc progressive springs in the front. The rear torsion bars are fine. No need to go to coil over. The added stiffness from the Koni's make changing them not really worth it. You should however re index the ride height in the rear if you get the Iboc's in the front. This makes a huge difference in how the car handels. Many people lower the frount and by doing this you are moving the weight forward. This can really make things ugly. Get the car back to level and then put it on a set of scales and fine tune it. BUT dont go more than a 1/2 inch in ride hight difference between the frount and rear trying to get the weigh corect. The adjustment is made on the trailing arms there are two bolts that allow for enough adjustment so you don't have to re index the torsion bars (that is a PITA).
Next go find some weltmister frount and rear adjustable bars. That is all you need to make this handle. The weltmisters have infinit adjustability. My car ended up liking then set dead in the middle of the adjustment range. I really dont think you need the camber plates but hay if they are cheep go for it. My car seems to be able to get enough camber with the stock set up. I am however using it for road course's. I would imagine autocross would require more camber.
I have the Koni's set full stiff and the bars are set almost exactly in the middle. This makes the car virtually neutral. I can control how it handles by how I set it in to a corner (by adding throtal or brakes or just letting off the throtal and letting it rotate.)
Dam do I ramble on. KEEP THE 944!!!!
EDIT: The motor can come out the top. I prefer doing it this way. You need an engine lift to do it. I think it is safer this way when going back in. If something goes wrong when re installing it the cross member will keep things from crashing down on you. You also don't have to mess with the frount suspension and the steering rack/shaft taking it out the top.