looking at buying a 3rd gen need your help!
 

I've owned my 1st gen for over 10 years, its the best truck i ever owned, 3/4 ton, manual RWD cummins. I now have a family and live out on a acreage so I'm in the market (moneywise) for a 3rd gen 4x4, crew cab 3/4 or 1 ton to haul gravel and my skid steer around (the 1st gen can do it but just its sketchy at best) but there is alot about the new trucks I don't know about. for example:
1) how do you engage the 4x4 on a manual transmission vs an auto?
2) Which one is more reliable the auto or manual?
3) is there anything I need to look out for when buying a third gen?
4) anything you would recommend?
5) Should I keep an eye out for the 6.7L vs the 5.9L? (seems the market is mostly made up of 5.9L)

your answers will be greatly appreciated!!!

The step from a 1st to a 3rd gen is enormous, and you'll be amazed at the performance of the new model. I'm just going to answer your questions in order, based on my experience with my '04 and that of various friends who have owned a few others ranging from '05 through '08.
1) 4x4 is either a lever on the floor or in the higher trim models a dial that actuates a motor on the transfer case. Pull the lever or turn the dial without any wheel spinning, and you're in 4x4. Doesn't matter if it's moving or stopped, and there are no manual hubs from the factory.
2) Manual, hands down. The auto isn't bad, but the manual is just better. Especially if you can find an NV-5600. If you get an '05 or newer with the G56 manual, you'll want to replace the dual-mass flywheel if it hasn't already been done. They tend to come apart and cause all sorts of havoc.
3) Tuners! The 3rd gen is all electronic controlled, so it's very easy to stack boxes and cause all types of mechanical failures from over fueling. Also note that all these trucks had a weak lift pump that feeds fuel to the injector pump. If it doesn't have the lift pump in the fuel tank, you're going to want to do that ASAP after purchase, because the pump behind the fuel filter on the engine is going to die. Guaranteed. Also note that injectors tend to stick with high miles and/or questionable fuel. Tuners make this worse because they can raise rail pressure which accelerates the wear on the injector needle. If it chugs white smoke on start up, or takes a long time cranking before it fires, or the oil is over-full and smells like diesel, walk away or know that you're going to be replacing injectors soon.
4) If you can find the original HO motor from '03/'04, the seemed to have fewer issues than the '04.5 and up, but honestly, the drivetrain in these is pretty stout.
5) 5.9 without question. Mostly because it didn't have all the emissions garbage on it, but also just because it's cool [guitar]

I really appreciate answering my question! I thought That manual might still be king, didn't know about the dual mass flywheel, or what to look out for if injectors are going!

question about the 5 vs 6speed, do you get better gas mileage with the 6? is the only problem the dual mass flywheel on the 6 but overall is it the better transmission?

Go for an early '05 with the NV5600 and no Total Integrated Power Module. '05.5 ushered in the TIPM and the Mercedes G-56 trans.
No issues here yet but it weighs on my mind.
A well serviced '03 or '04 is great too.

I chose the 03-05 model because I preferred the front end look (The 06 and up look different), and slightly better mileage (maybe).

I too jumped from a 1st gen to 3rd, zero regrets.

Only downside is everything is more expensive and a little more difficult to troubleshoot.

I have been in the 12 valve section for almost the 9 years I've owned my 1994 std cab, 4x4 diesel Ram... Last weekend, while driving though a town in western south dakota, I saw a nice looking crew cab, in one of the two colors I've been looking for the last 3 years. i say 3 years, because I've been watching the market & those suckers are expensived..lol. Told the wify lets just stop and look/see..bad move. It was fantastic, clean, low miles 121,000 & appeard to have a lot of extras..which later I found out the seller spent a smal fortune on. Edge module, air shocks, rear bags, plus +.. I was tired of the 94 with no room inside the cab, small things starting to fall apart, etc. I kept up on the service/naintance by doing most everything myself. I called the # and he said he just bought a new one, & need to sell this one..it had some storm damage on it, so I told him I'd think about it overnight..talked with my wife about it a little and the next morning we went back & did a test ride..bingo..that was I I needed, the smoothness and power was incredible!!! put $ down on it and came back a couple days later...I too need to read and find out the do's & don't on this one..meanwhile, I have had for sale a 94, std cab, auto, with Boss V-plow lol...

Oh yea, I made SURE the vin number 8th letter is a "C" and not the "6". mine IS the HO one... (not that the 6 is bad)