You got it in one.
You will see when you do the job. The top nut is not only tight, but pretty awkward to keep the socket seated properly. The single hex just gives you that little bit extra help. My advice is to try getting the top nut off first, because if you cant get that, there is no point to the other two.
You will need to disconect the power cables to the starter to make room though.
If... no.. When you get angry, and try to aproach it from the top, becarefull of the coolant line that you will have to push to the side. They snap before the bend.
Oh, and if you have a second person available it will make it easier. Use the second person to come in from the top to hold you extension bar square on the nut.
Make sure you have a breaker bar also. There really is no room to get any leverage.
Dont be put off by my posts, Im about as novice as it gets when it comes to mechanics.

