If you have the head off, don't need to remove the rocker arms if you have a "C" shaped valve spring compressor. There are many opinions about removing and replacing the valve guides, covered in another thread, recently...look for it. The main thing though, is the heat...got to be hot...like in the bake oven and the guides have to be frozen in the freezer. The only time I had to remove the rocker shafts, was when a valve seal popped off, and I reseated it with the head still on the motor. It's a tricky job anyway, with all the washers and such. Just use the valve spring compressor from one of your car repair buddies..it will work fine if the head is off. Any time the guides are replaced though, it may be that you will have to get the valve seats recut....some claim they can do it, but it is hard to get the guides perfectly installed in the same angle/position as the ones you are replacing. Have fun!