There are several Ram Diesel forums, I usually go to
ram1500diesel.com for info specific to my ecodiesel. I visit this forum for general Ram info.
I'd first try to find out if the truck has a tune and how long it has had it for. This generation of ecodiesel engine pulled sooty exhaust back to the intake through the EGR valve and most tunes turned that off. The soot is commonly blamed for wear on the engine as it quickly gets into the oil. There have also been a few clogged intake manifolds though a leaky EGR cooler in the EGR valve may be needed to really make the soot build up (see my mention of the EGR recall below).
If there's no tune I'd look to see if the engine was replaced and when. If the engine was recently replaced then the intake manifold is probably pretty clean, if you are in a state where you can get a tune that addresses the EGR then you'll be well off.
There's a recall for the EGR and another for the tone ring, if the EGR recall isn't done I'd pass unless the engine was recently replaced. Both recalls should be done quickly if they aren't already completed.
Outside of the engine, everything else (I think) is shared across the other Ram models.
If you are used to the Hemi I'd suggest driving the truck around town, making sure to do it at least once when the engine is dead cold. When cold there can be major hesitation when trying to merge onto a fast road, something the Hemi's don't do. I installed the OEM remote start so I can give it plenty of warm up time.
Lastly, I'd ask why you are considering the ecodiesel? If it's for the better highway mileage or less maintenance then this may be a good change. If you are looking for a bulletproof diesel engine to go 500,000 miles or more I don't think this is the right truck, these little ecodiesel motors are not Cummins replacements. If you haven't owned a diesel recently you may also want to check the availability and cost of diesel versus gas. The cost of diesel in CA is usually the same as or more than gas, I drive so many highway miles though that I see much better fuel economy than I would with a gas engine and the cost difference works out in my favor. After getting a diesel truck I've realized many stations have diesel though not all of them.