What Tex_77 told you is spot on. I normally set temp at 250 whether smoking or by oven. Get yourself a good thermometer. Definitely pull at 120 and set oven very high to sear, and pull it out and loosely wrap with foil. Let rest at least 20 minutes. Remember temp will rise at least another 5 deg searing and 5 deg resting. Usually finished temp is 128-131 for medium rare. No need to inject prime rib. I always put a rub on 2 days prior to cooking it.

I have an old analog dial Smokin-It #3. It’s similar to CookShack. Much cheaper and it has been very reliable. I cut my snack sticks to length and smoke to 165 degrees. I have other smokers and this is all I use. Nice not having to attend the fire. I also have the cold smoker attachment they make. Quality all the way. I’m seriously thinking of getting the digital #3. They’ve gone up in price since I purchased mine but I would like the higher temp compared to my 250 degrees.