Your best bet is to hook up with a local 4x4 club. Not only do you get the commeraderie of fellow off-roaders, but you also get to learn the location of all the good trails. On top of this, it's always a best practice to 4-wheel with friends so that, if someone breaks down or gets stuck, there is someone to help.
I don't know of any clubs in Northern Idaho or Eastern Washington, but I'm sure there is something up there. I have both a Trooper and a Jeep, and I love both of them.
I could show you some good off roading trails, but you gotta promise not to shoot the wolves! If you want to hit some hardcore mud and crud, turn left or right, along the rail road right of way off of Davis road up in Sagle just after spring thaw. You'll get your fill of off roading!
If you take Sherman avenue out of town at the East end, it goes by Fernan lake and continues out to the Canfield shooting range, and you can turn right at the range or continue up the mountain to the top. The high drive is out by Silverwood, off to the right, by a place called the "Lil brown jug" probably now gone or name changed, I'm sure. A bit of a drive but you can travel for days up there and never see it all. There are other places around you, probably even closer to you, but these are the places that stick out in my head that were enjoyable to me back in the 1980s. Get on Google earth and check out these two locations though. It's worth a look that way at least, from your computer chair! Now I only off road to go and hunt for firewood just down the road a patch here in lovely Vay! If you go, be sure to take some binnocs, a map, and a camera, so you can share the journey with us!
i'm hopefully getting stationed at mt. home this fall, how are the trails/how far of a drive are they in that area?
well you can drive about 30min to the east, to GOODING, ID there you have Bennett hills, i got there every spring, because the trail is different every year (due to snow melting) its not bad, its usually me, my dad and his brother, they are in stock cherokees, and im in a lifted cherokee. But they scrape a lot.... lol
but still an awesome trail, there is lots of pictoglyphs from the indians. on the rock ledges. plus theres the 'little' city of rocks.... but it takes us all day to do the trail....