You can check out Garmin's map products by using their online map viewer. Here's the link for their City Navigator North America 2009 product.
https://buy.garmin.com/shop/shop.do?...56#coverageTab
There is a link on that page to view the map interactively. You can pan and zoom to find the areas of interest and see if there's enough detail.
They also have topographic maps that might be interesting to you. You can select the map product then click on the "View Map" tab to check it out.
Microsoft
Streets&Trips, iNav
iGuidance and Garmin City Navigator North America all use the same map data supplier, Navteq, for their map data, so there is little, if any, difference in the map details. So looking at the trial version of Streets&Trips will give you an excellent idea of whether current road map data is suitable for your purposes or whether you need to explore the possibility of regional topographic maps.
Be aware that, although the map data comes from the same supplier for all three of the vendors mentioned above, the navigation programs from each vendor are hugely different in how they display the map data (iGuidance and Mobile PC have similar looks and are very different from Streets & Trips) and also the features and functions they have (look through some of the reviews on here).
If you are planning a multi-stop route, Streets&Trips is the only one of the bunch that will allow you to ask it to optimize a route amongst multiple stops to find the most efficient driving route. That is, you can select a list of places to go in any order and then ask Streets&Trips to optimize it. The other two (perhaps all the other competitors) will only calculate a route in the order you list the stops. If you enter the stops in a random order, the resulting route might seem like someone spilled spaghetti on your screen.
If you want to avoid the usual direction these threads go, ask specific questions about how you want to use a navigation program. Most people just ask open-ended questions like, "Which one is the best?"

Well ... ummm.... errrr..... ahhhhhh.... "best" for what sort of use?
The only sensible answer to questions like that is, "It depends on what you expect/need to get out of your navigation program."
And recognize that the final answer, for you or anyone else, is going to be a combination of the map data detail and the nav program features and functions. One without the other equals zero.
One final thought... I live a little ways north of you -- about 120 mi straight north of Plentywood. One thing I've found with Navteq's road map data is that it's pretty good in areas with large populations and not so hot in more sparsely populated areas. This applies to all three products mentioned above (I have all of them). So you are on the right track to check out the map detail first. All the program features in the world aren't worth spit if the details you need aren't on the map.
Holler as detailed questions come to mind.
...ken...