Been to Tog once and loved it, so far the benchmark sled trip!! We will be going back. Last year we did West Yellowstone/Island Park. If we go to that neck of the woods again I think we might stay in Island Park, it's not that far from West Yellowstone (right over the pass) and it has many more available trails if you want to trail ride.
We did go through Yellowstone Park and I could have sworn that I saw Togwotee sleds there. That said, you could just drive from Tog and rent in West Yellowstone. Check (I think this is what it's called) Two Top Snowmobile Rental, they have a website by that name, they are located literally a few blocks from the gate to the park, we had an awesome guide.
A bit of advice if you go into the park. There are two loops you can take. It was suggested by someone in our party that we do both loops just cuz we migh not get back there. Sounded good to us. You do get see a lot more but if you want to spend anytime at any given place you are very limited as both loops is something like 130 miles combined and they want to be out of the park at like 4:30.
If you want to do both loops, I would highly suggest doing one, one day and the other another day. But by all means do go into the park.