Nicholas Kliewer wrote:

I live in Dallas, TX and don't get out of the flat lands much.
This Fall, I am planning a trip to Oregon in a C172 and figure
that I could use some mountain flying training.

A mountain flying school like those recommended here are invaluable.
Having said that, a 172 has its limits, far more so than a 182. But,
you can safely fly a 172 from Dallas to Oregon in the summer provided
you select airports that are not too high and have fairly long runways.

You also want to avoid terrain that requires flying much above 8,500
west bound and 9,500 east bound. With a little planning, that's easy
too. Since you're going to COS, you best stay on the east side of the
Rockies until you can go through the lower, less mountainous parts of
Wyoming.

Also, takeoffs in the early morning at any airport above 3,000 feet,
MSL, is like money in the bank.