150' Norfolk Pine in Backyard and growing...help!

Hi,

I need to maintain a very large Norfolk Pine tree in my back yard, and
I'm not sure what the right actions to take are. Here are the details
(see the bottom for my questions):

My backyard contains a large (~150 feet tall!) and seemingly healthy
Norfolk Pine tree that is growing at an alarming pace. When I bought
the house 3 years ago, the tree was covered in ivy (it was reaching
about 50' up the trunk). Thinking this was not healthy for the tree, I
cut the ivy down. I'm not sure if that accelerated the tree's growth,
however since then it's branches have grown to cover the entire back
yard (about 15-20 feet broader), and the tree keeps getting noticably
taller each year.

I have at least three reasons for wanting to cut back the tree and stop
its rapid growth:

(1) Because we are in San Francisco, back yards are not very big. If
the tree were to fall, it would severly damage either my house or one of
the neighbors'. I've been told that Norfolk Pine trees have shallow
root systems, though this tree seems to have been here for 50-100 years.

(2) There is no longer any sun in the back yard.

(3) Every 4-6 months, the tree "sheds" its "leaves", and covers the back
yard with 6 inches deep of "droppings" (these aren't really leaves, but
I don't know what they're called).

My questions:

I've heard that if Norfolk Pine trees are pruned incorrectly, they never
regain their shape, and it can also damage the tree. Is there a
"right" way to do it? How do I know if a local "tree expert" knows what
he/she is doing? How dangerous is a 150' Norfolk Pine tree...do they
have a height above which they fall more frequently? Can I trim the
lower branches without damaging the tree?

To make matters more complicated, there is no access to my back yard for
any sort of crane, since the widest access to the back is about 3 feet
wide. So, any sort of tree maintenance will have to be done manually,
with someone climbing the tree. Is this even possible???

If anyone has had experience with a similar-sized tree, please let me
know!

Thanks,

-- Fred