Only God can trim a tree

We've been fretting over our big tree for some time now.
A couple of years ago the fellow we hired to trim and shape our cherry tree told us he thought we ought to cable our 20-year-old cottonwood out back.
It's grown quite large and has a split trunk with three large branches growing out of that trunk.
We love this tree as it provides shade for the entire backyard and its leaves rustle in the afternoon breeze quite pleasantly.
We weren't sure we wanted to cut any of it out but we told the tree guy we'd consider it.
He went off to check on prices.
When we didn't hear from him for the rest of the summer, we were actually a bit relieved.
This summer, however, a couple of smaller branches broke off during a particularly wild windstorm.
I dug out the tree guy's number and called him up.
I had him come pay some attention to our shrubs and asked him again about the tree.
He said he would see what a sling would cost and call me.
"You'd hate to have one of those branches fall on your roof," he said.
That's been several weeks ago so I called him up again.
"The best price I found is from a place in Canada," he said. "But I'm a little tight on my finances right now so you'll need to call them and order it. Then I'll come cut off the branch and install the sling."
The sling would be about $300 and the branch removal plus placing the sling would run between $700-$800.
Um.
I know nothing about tree slings.
What size? What color? What do I ask for?
The tree guy told me to get a 4-ton sling with a 50-meter cord.
I gulped.
But I did make the call and was doing fine until the girl on the other end of the phone realized I was calling from the United States.
"We only ship within Canada," she told me. "You'll have to pay the freight costs. You might want to consider a company that's more local to your area."
Um again.
I rang off and told my husband the situation.
He was not impressed.
"We don't know what to get and we shouldn't have to get it ourselves," he said. "Let's think about this some more."
I called our neighborhood landscape man who said he would come take a look.
He came by yesterday.
"I don't think it needs cabling," he said. "It's a healthy tree. It looks fine."
OK.
Since I'd rather not spend $700-$1,000 to have a branch cut off and perhaps damage an otherwise well-behaved tree, I think we'll go with the second opinion.
Let me know if the wind starts blowing.