You made no mention of what your truck is...gas or diesel, but you do have at least some experience towing in the mountains. The one thing I would offer up to you is that this trailer is obviously going to be much heavier than your previous trailer when towing. Then add in the "towing in the mountains" part of if and it will be a similar, yet different experience because of the added weight and length that you will be towing. Know exactly how to use your truck to be able to maintain a safe speed when going down the mountains. That could be a combination of proper lower gears and or engine braking via a diesel engine.
If you are strictly referring to the actual navigation part, the RV specific GPS is a valuable tool. Another "tool" that I just discovered that others have probably known about for years is the "Mountain Directory" Here is a link to their website....
Look it over and it may be something you are interested in. They even have a "Try the demo" on that page so you can get a feel for it.