Relief is very easy to check. Simply put on a capo on the first fret, then press the low E string where the neck meets the body. Probably at the 14th. fret. You have now created a straight edge and can measure the gap between the fretboard and the string. If you have two capos use them at both points, it's a lot easier. A feeler gauge will give you an exact reading, but just looking will probably tell you if you have an excessive amount of bow.