With both heads already going to be off, I'd consider it more than in my own case, but it would add all the complication of having to remove the oil pans and that "fun".

As far as the sticking allen screws go, if you start to strip one, I can't recommend the "impact screwdriver" tool enough. It's a handle with a 3/8" or 1/2" socket drive on the nose, and a hammer stiking surface on the rear. You put on the bit appropriate to the job, or a socket in this case, turn it the proper direction as if you were going to unscrew the fastener, and whack it with a large hammer. It helps to jolt them loose, rather than just stripping the head out (as I managed to do to a couple that were seized, on my engine project. Oops!)

Another fine wrenching friend is a good penetrating oil, as you most likely are well aware!

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...