I am going to assume are not that familiar with towing a trailer, so I apologize if you already know this info, and I mean no offense at all.
Towing in the mountains puts extra strain on your entire vehicle, from transmission to brakes to cooling system to electrical system, so be aware of how hard your Caddy is working.
Check the owners manual for information on towing with regards to 'overdrive gear'. Some manufacturers recommend that you don't tow in overdrive.
Brakes have the toughest duty in the mountains. Use them sparingly, and if you are on the brakes more than 60% of the time, stop every so often and let them cool. Experience is the best teacher here. Get used to shifting into a lower gear on the downhill run, and keep your speed 5to 10mph below the posted limit. This will give you a good safety margin, and when your speed gets to the posted limit, put a little more effort into slowing down. That way you will hopefully never let it get going too fast. Use the engine and transmission to keep your speed steady, and use the brakes when it starts to creep up. DON'T RIDE THE BRAKES FOR LONG PERIODS. I can't stress that enough. Brake failure in the mountains is a bad thing. If you stop, get out and walk around and touch the rims to get an idea how hot the brakes are. The will be VERY warm, but you should be able to touch them. If you can't touch them, let them cool down for 15 minutes or so. If you smell a strong burning smell, or see smoke coming from the wheels, you are going to sit for a while. Then proceed very carefully to a place where you can check them for overheat damage.
Make sure your engine coolant is full, your radiator is clean and unobstructed, hoses and such are in good shape. Watch your temp guage going uphill, that is where your engine is working the hardest.
Don't get in a hurry. Going uphill, put the transmission in a lower gear (to make it easier for the engine to pull the heavier load) and keep your speed down. Don't worry that everyone is passing you. Be courteous and pull over every so often and let the cars behind you pass. It gives both you and your rig a chance to relax for a few minutes. Going downhill, use the same gear that you did going up, and keep your speed the same as you did climbing the hill. If you get going too fast, bad things happen in a hurry. That trailer is trying to push you down the hill as fast as it can, don't let it.
Always try to err on the side of caution with regards to speed and distances. Less speed, more distance. Just keep in mind that you tow vehicle is working harder, and responds slower with the trailer, and you should do fine.
Again, I apologize if this is condescending, I don't know how often or how much experience you have pulling a trailer, and I wrote this for someone that has very little of each.
2013 Voltage 3905