To measure the crank, any half decent dial caliper or digital caliper will get you close enough. You want to look at the crankshaft section of the page you linked, main bearing journal size and rod bearing journal size, these two will tell you how much if any your crank has been ground. The other diameters listed are bearing inner and outer diameters, these are set by the bearing manufacturer. Most aftermarket bearings are marked with a date and size, example 2/87 STD, February 1987 , standard size. You likely will find a manufactures name also.
Most cranks are only ground to .020" undersize, .030" is pushing it, the hardness applied from manufacturing only goes so deep into the metal and most stop at .020" to stay in the hard surface. Not sure all that is true, but it has been told thousands of times over the years.