The Hwy, through Lincoln is actually quite nice, we travel that way quite often, Deb's Uncle lives in Lincoln and we go down to visit him a couple of times a year, are you thinking of taking 200 up to the park?
Anyway, it is very easy to travel, with nice sights along the way.
We'll be up in Great Falls and Choteau and may come down that way...still deciding if I can stand missing a day or two in YNP. I had also wanted to check out the Three Forks area and then we'd come up through Missoula. I have this huge chunk of time but still can't fit in everything I want to do!
MT200 from Great Falls to Missoula is a pretty route. The road is fine but does get quite winding along the Blackfoot River as you get close to Missoula. I've never cared for the Garrison to Helena road. The road itself it fine but the Garrison end is ugly.