Use the recommendations in the owners manual, where applicable. Different plug manufacturers may use different gaps? Some type spark plugs you don't gap, the gap is pre-set.
.043 gap should work ok.
Try your local library, they have access to many online service manuals that require a subscription. Its free to access them all, but you can only get access to them at the branch.
easy,take of the shaft,take off the ouside,after it is easy for the inner one,replace homcinetic,fill up with appropriete animal grease,yes the speciazl one you buy is really animal grease,with a black colorant,
and reassemble all,
should be done in about 2 hours max,
Usually if it's blown between the cylinders it will have white steam out of the tail pipe. If it's crack between the oil and coolant gasket holes, you will have coolant entering the crankcase and your oil will have brownish sludge. Look for signs of coolant mixing with oil on your dipstick.
The check engine light will stay on until you fix the problem sensor that set it off.. Do not ignore it as it will cost bucks especially if the fans is not working. Once the problem has been fixed you will have to reset the CPU by using a code reader to put the light out.