A lot of advice here, so I'll just throw in some more.
"80% rule". This is a "rule of thumb" that many use when considering tow vehicles and trailers. Don't go over 80% of the tow vehicles tow rating. If your TV can tow 10,000lbs, don't get a trailer that has a loaded, or gross, weight of over 8,000lbs. This will give you plenty of "cushion" with your TV, for the weight of passengers and stuff in the bed of the truck (like firewood!), weight can add up quick. Yes, you certainly can get a trailer that weighs in right at the limit of your TV, but the truck will be working hard.
Engine size. In general, even with today's smaller engines that are rated for more power, the bigger the engine the BETTER the fuel mileage you will get towing. Yes, big engines get lower fuel mileage driving around town empty, but when towing, you still can't beat cubic inches (showing my age... I guess I should say liters!). Diesels are expensive, but wonderful for towing, and get great fuel mileage while towing compared to gas. If you are trying to figure out costs and value for the dollar, it will take years to "pay off" the cost of a diesel engine. If you tow a lot, diesel IS certainly worth it. A big gas engine, like a Ford V-10, will get better fuel mileage while towing than a smaller gas engine (it may not make sense, but I've found this to be true time and time again). That may be something to think about if you are not towing a lot... get a big gas engine.
Crew Cab. If you need the seating room, look at pickup truck Crew Cabs! LOTS of room, and you still have the bed of the truck to put bicycles and firewood in. That is why we just got a 2008 F250 CrewCab with a short bed... I needed seating room for my family -- and the "short bed" on a full size pickup truck is still pretty big. Someone else mentioned getting a CrewCab with a full size, or 8 foot, bed. That is a BIG truck. Same with Dodge MegaCab -- BIG truck, but the cab has SOOO much room! The rear seats even recline!! You have lots to look at and think about.
The Suburbans and Expeditions are very capable vehicles, just make sure they have the "tow package". Pickup trucks usually have stronger and stiffer suspensions, which make them arguably better as tow vehicles, but the big SUVs work fine.
New trucks... You can get a brand new 3/4 ton CrewCab pickup for under $30,000. Go into a dealership, planning on NOT signing papers that day. Don't worry, trucks will still be available the next day (lol). Dealers really want to get these trucks off their lots, be stubborn, the price will keep falling for you. Scrutinize the manufacturer's websites, I found a couple things that my dealer "didn't know about", that further lowered the price of my truck.
Also, I really think that the present "slump" in truck sales is going to turn around, maybe starting next summer. Just guessing here. This is a good time to buy new. Something else to think about -- My previous truck I bought used, in excellent condition, at a great price.... but... 3 years later, I still owed payments on it, and I had an 8 (eight) year old truck when I went to trade it in. I know you can get used trucks for a great price, but just remember that in a few years, you will have an old truck.
You have a lot of information here to think about, and a lot of information available to you on the internet to peruse. Try to take your time, and don't get yourself too worked up.
Hope this helps some, and good luck!