Camp and route to Yellowstone?

[strawberryjo]

Hi all,
my wife and I are headed east to yellowstone for a short stay.
We are coming on Hwy. 12 to Missoula then I90 over to the bozeman/livingston area.

So, question, any reccomendations for over night in missoula. One night prefer ele.& water, but boondock is o.k.

Also which route would you take down into the park from the north?
287, 191 or 89 ? rig dosen't like the heights.

Thanks in advance,
Joe