If you're anywhere near Chicago, I-80 west to just before Omaha is a good run, and follow I-680 west to connect with I-29 north. Take that to Sioux Falls, Iowa and catch I-90 all the way To Seattle. Easy run.
When heading home reverse the trip.
On the way back, when you get to Livingston, MT, take US-89 south into Yellowstone, to US-191 south to the Tetons area.
When done with the Tetons, sty on 191 South to Rock Springs, where you can take I-80 all the way back to Chicago.
If you're in Southern IL, Head west toward KC on I-70, and again, take I-29 to Sioux Falls.
or follow I-72 west toward Hannibal, MO, and US-36 West to St Joseph, MO. Again, I-29 to Sioux Falls.
IF you're more interested in Portland, then stay with I-80, into Utah, and take I-84 up to Portland.
To detour to the Tetons, Look at (again) US-191 at Rock Springs, or on the way back, at Mountain Home, ID, take US 20 and 26 eastbound to Tetons area, and US-191 South to Rock Springs.
When you say you are not "seasoned" does that mean you are not experienced with mountain driving with your 5er? This could be a show-stopper, because the routes have some serious hills to contend with. Nothing that can't be handled, but caution is recommended. The biggest concern would be US-26 between Idaho falls and Jackson, WY.