I have a 2012 I bought new and have had very few issues, but I'm only at 63K miles.
RAM is a great truck and should give you reasonably trouble free service for some time to come.
Engine and trans should be good as long as maintenance was regular.
Part of regular Hemi maintenance is changing spark plugs every 30K miles. If private sale, ask owner how many times they've been changed.
**There are 16 plugs not just 8. Good trick question if he says he does his own maintenance or you are suspicious: "So how many are there, 8?"
If a dealer, ask for maintenance records, or at least a summary of what they have done to it, and if a Dodge/Chrysler/Jeep dealer whether there is a record of dealer maintenance by VIN.
If you have a mechanic check it, ask them to look into the throttle body to check for build up on the underside, and also pull a couple spark plugs to see what kind of plug changes it has received. Build up on the throttle body could cause rough idle or sluggish response later. Old plugs give you an idea if it was maintained. Also have your mechanic check the age of the fluids in diff and transfer cases. If its old it probably did not receive the frequency of maintenance it should have. All the underside fluid should be changed around 60-65K miles and again at 120K.
Some other items:
Listen for Hemi tick. Injectors make a certain amount of noise like plastic parts ticking, but the Hemi tick is fairly high in the engine from the lifters and sounds like metal tapping. A lot of Hemi engines have it and it can sometimes be treated with better quality oil.
Also listen for a tick on cold start that quiets as engine warms--that would be a broken exhaust manifold bolt(s)--not a show stopper, but you need to lower your offer for the repair you'd have to pay for.
Check up under wheel well liners, both front and under the bed to make certain fenders haven't started rusting on the inside considering PA is salt town USA.
