Rockers are super easy. Not sure about the S2, but the front valve cover can come off in as long as it takes me to break out the 3/8" socket. The rear requires removal of the EGR Valve and PS Pump. However I have done both of those so many times, it doesn't take me longer than 5 minutes for the rear valve cover. This is just to remove it, not to do rockers.. that takes a little longer. I'm assuming with the rockers you are also going to replace the springs? Have fun with that
. My retainers were stuck in there good, and it took quite a bit of effort to get them out of there. And they fought the whole time putting them back in too.
Again, because I have done it so many times, I can pull the entire exhaust off my car in under 2 hours. However, you must raise the car to get to the rear header to rest of exhaust, then you must drop the exhaust [two rubber hangars at about the middle of the car-length]. I couldn't get any of the exhaust pieces to come out under the car, they all needed to go up. But again, this could be different for the S2.
I'm not sure about the kit pdad is talking about. I think it would just be easier to bring each cylinder to TDC. That way the valves don't fall in.. that would suck.
Okay, I feel generous this morning. A little tip for removing the spring retainers. Get the little arms that go in the springs as low as possible [not quite all the way down, you'll know]. Then compress the spring as much as possible, and push DOWN to increase pressure, then rock the valve spring compressor around and the retainers SHOULD come out. I didn't need a magnet, because mine were really stuck in there. No need to put a lot of pressure rocking, but pushing down you need quite a bit of strength. Not sure how easy that would be considering the heads are on the car, but when off the car, it was pretty easy.