It is worth doing the homework to at least understand the basic weights and forces involved. I won't second guess the manufacturers and I'll reserve comment on anyone else's comfort with their towing setup. I will agree with other posters that you can't necessarily rely on RV salesmen for useful or even correct information. Some salesmen will flat out lie telling you anything they think you want to hear, but most just aren't knowledgeable enough themselves.
It is also worth doing the research on what options affect towing and how certain options can improve the towing experience if you are looking to buy a new tow vehicle.
There are lots of resources on all of the weights involved and how they affect towing. There are several weight ratings that should be taken into account for safe and comfortable towing, but when you boil it all down, for the most part there are two weight ratings that are usually the limiting factors. First, is the overall weight. Your trailer fully loaded as it will be towed added to the weight of the tow vehicle and its contents needs to be under the GCWR (gross combined weight rating) of your tow vehicle. This is often much easier to satisfy than the next weight limit.
The weight limit that is far more often a limit on what can be towed is the tongue weight. This is the downward force put on the hitch ball (therefore the rear of the truck) from the tongue of the trailer and is usually around 10% of the trailer weight. The tongue weight along with the weight of the vehicle and everything in it including fuel and passengers must be below the GVWR (gross vehicle weight rating).
Vehicles are rated and capable of pulling a lot more than they "haul". This is the limiting factor that pretty much eliminates 1/2 ton pickups from hauling pretty much any fifth wheel. There's an ad Ford recently put out showing their upcoming electric F-150 "towing" a 1.25 million lb train. However, even a cursory look at the video shows several flaws in this story. They use a single web strap to hook the train cars to the truck. The train is on flat ground and obviously on a train track. They also don't claim to be able to stop that weight.
You indicated you already have the tow vehicle. There are many variations of the 2006 RAM 1500 4x4 with payload capacities (GVWR - curb weight, the weight of fuel, occupants, added stuff, and trailer tongue weight) ranging from ~1000 - ~1700 lbs. The max towing capacity (roughly GCWR-curb weight) ranges from ~2900 - ~8700 depending on the specific model. See
this link for actual values.
If you are considering a new tow vehicle, there are options that can improve your towing experience. Factory installed max tow packages can be good values. These can include beefier radiators and factory installed transmission oil coolers as well as factory installed heavy duty trailer hitch receivers. Air ride suspension can improve the ride and improve the ability to keep the truck level with the added weight of the trailer tongue.
Regardless of the tow vehicle, the hitch used to hook it up can also have a profound impact on the handling. I've been happy with the equalizer weight distributing hitch, but it's the only weight distributing hitch I've used so I have nothing to compare it to.
If you carry any significant weight in the trailer, the way its loaded can also affect how the trailer tows. Weight added to the front of the trailer increases the tongue weight. Weight added to the back of the trailer decreases the tongue weight. The tongue weight in relation to the overall weight of the trailer affects stability while towing. There are a lot of people with a lot of opinions and some real religious zealots when it comes to weight and towing. I fall somewhere in the middle. I believe its worthwhile understanding the affects and making an informed decision about how to proceed. There are many lengthy threads on this topic most of which devolve into arguments but many are worth reading.
With respect to the most important question to ask RV salespeople, I don't think there is one. I would do my homework here and other places on the web. I think its worthwhile to visit as many places as possible to see as much as you can without pressure before making a decision. RV shows or just walking local RV lots can be good ways to see lots of RVs. At first just tell them you are just looking, maybe pick up some brochures, but most of them are available on line these days. Do your research ahead of time and ask any questions you might have, but don't be surprised if you've read the brochure and know more about a particular unit than your sales person.
Once you have specific questions, come back here and search the forums. If you can't find the answer, ask a specific question. Most here more than willing to help...