2nd gen, say around 100k miles (I know, the cummins can go a lot lot farther than that)

what should I look out for?

 

need more info...

auto/manual???4x4/2wd???what you plan to use it mainly for...

 

auto
4x4
commute, occasional hauling and wheelin

I need the room inside of a big truck.

 

The Dodge/Cummins combo seems to work well for commutes. Depending on the version of the motor there are some things to look out for there. Other than that its like bying any other used truck, Check for hitches, dents in the bed to indicate heavy hauling. There is alot to read about here.

 

i read on here, that it runs better when you tow a heavy load and put the engine under some stress

?

 

No doubt about it, the cummins loves to have something to work against. It still runs fine empty, but put some weight behind one, and it really starts to shine!