I have hunted Newfoundland and Alaska. I booked the first hunt through an outfitter agent for the Canadian hunt. Newfoundland in the late 80s was alive with game. I don't know how it is now.
My first trip to Alaska was booked straight through the outfitter. He was know through mutual friends. It was on the Alaska Peninsula and we were again in the middle of good game country.
The first hunt I ever booked was in Quebec. I chose an outfitter guide out of the back of a hunting magazine. It was a disaster. I ended up guiding my guide back to camp. He had no idea how to even use a compass. He got lost the first time within a half mile of camp. The cabin was built out of short logs and chinked with sphagnum moss. Half the rodents on the tundra were living in my mattress. He was building a fire in the camp stove, a home made contraption constructed from a grease drum. He had a squeeze bottle of Colman fuel and would squirt it into the fire. Then he would laugh and do it again. One time the fire came back and caught on the bottle, he looked around from side to side in panic, all the while dribbling fire across the floor and under the bunks. I didn't let him do anything after that except wash the dishes. To top it off the area had been over hunted for years. Oh I forgot to mention he didn't speak English. It was a valuable education though and I had a good laugh at my own expense.
Unless you know someone personally that can vouch for your booking agent or they have an impeccable reputation you won't know what to expect. I would tend to think Cabelas to be on the up and up. Buy all means get multiple references. Even the best outfitter sometimes misses the migration, make sure they will relocate you if the area does not hold game.