its imperative that in preparation for this job you should have a knowledge of mechanics (buy a manual at least).
after having had the cylinder head checked repaired & resurfaced the cleaning of the cylinder block deck must be done with care, a razor blade to remove gasket without scratching then a honing stone (just like the one used to sharpen axes or knives) soaked in oil drained then in rotational movements always keep turning & altering the stone so as to not wear a pattern. dont use a mechanical sanding disc or such as these tend to machine a leading edge around any ledge. you may not think it would hurt but the relaxing of the tension on the gasket around this ledge is enough to cause a failure of the sealing gasket again & too much will result in the need to remove & strip the engine for the cylinder block to be surface ground which is way more work than necessary in most instances. i also believe the use of a head gasket sealer such as copper spray will take up any minor variations in the sealing faces whether it be the block trueness or otherwise but please a little will go along way ,a lot will go all the way into bore galleries etc so use it sparingly a smear is all that is needed. dont forget to clean & oil up your head bolts (again only a smear of oil on the threads (not in the holes) & under the bolt head face & if they are torque tension, as opposed to angle tension, retension them (the head bolts), the head gasket may be a non retorque type but the block threads, head bolts & alloy head may relax together enough to cause a failure, when you go back to the supplier they will tell you its fuel, temperature, fitter etc you will be lucky to get a smile
cheers hope this helps.