Since it was a pickup in my case, mechanic was able to find a few open holes between radiator/grille and bumper..
MH chassis?
May be not so easy, lots of junk going on in there, being MH mechanic is not for me.
I believe a 13 mm six point socket IS recommended for this operation, 12 points do not have as much grip (less contact area) and you need as much contact area you can get.. I used a 6 point but since I didn't try the long extension route my ratchet was hitting the block or other obstructions which made it very difficult to keep in line with the bolt head.
HERE is an article discussing the replacement on a 5.4. There are a couple of pictures which may help show you what you are up against.
While that link discusses a F150 5.4, you mileage on how much space you have for wrenches varies a lot depending on yr and model.
By the way, the top bolt, you cannot see, you have to feel for it..
While I would not say it is an impossible job to DIY, it is more of a pain in the rear, hands, arms and possibly eyes and a time killer.
It can be DIY, but you are working in an extremely close place, top bolt cannot be seen and you will need a collection of different length extensions, possibly several different 13mm sockets (standard and deepwell), a universal swivel and a few bandaids for the leaks you will develop and if you are drinking man, a few six packs..
But all it takes is just rounding off one of the bolt heads to ruin your progress and your day and that is a real possibility.