How to test a direct ignition coil

Ok here is the deal I have a 2004 isuzu rodeo with the 3.5L motor the motor went out on me so I bought another one which isnt cheap by the way and went to a small town mechanic to put it in well he put it in and now its reading p0300 code which means multicylinder misfire and I called him back and he is saying 3 of the 6 direct ignition coils are bad if this was the case wouldnt it read multiple codes for each cylinder so I want the old coils back to test them but I need to know the specs and also how to test them need to know if I can ohm them out if I can what is it suppose to read