8 screws hold the filler neck in place, 4 holding the ring to the tub and 4 holding the neck to the ring. There may also be a ground wire connecting the filler neck to the tub. It would be inside along the neck.
Rear Skid Bolts
Behind the bumper on the bottom of the frame you will see two brackets with 3 bolts on each
The middle one is the tank strap and you wont need to loosen or remove that, but the two outer on each will allow the back of the tank to fall downwards. Have a jack under it.
This is where you may be able to cheat.
If you can let the tank swing down enough you may be able to reach in and get at the regulator. I was able with my factory skid plate.
note* To keep it from bending up the skid plate too much you may need to loosen the bolts on the inner side of the tank.
Front Skid Bolts
there are two on the drivers side
you can kinda see how the lip of the skid plate sits above the rear sway bar. If you end up dropping it all the way you'll want to hug the rear as much as possible at first to avoid getting it stuck on there.
one on the passengers.
(its getting dark out already so it was kinda hard to get a pic)
To drop the tank completely just pull the nuts off those 7 bolts and it will come straight down. These are carriage bolts and hang down from the frame and a support member. If they are stock they will be rusty and you may want to replace them.
I recommend putting a 2x4 on the top of your floor jack to allow you to slide the tank around and give you the wiggle room you might need.