Welcome to the boards, a couple of things regarding a diesel:
Radiators on 2008 trucks (later years even), especially on the earlier 2008 job 1-2 trucks will eventually leak. I believe it's covered under the 5yr/100k warranty now but you're almost past that.. The radiators are not cheap due to their size (around $1000 installed), I'd really suggest planning for a failure and going with an aftermaket one. There should be a tee near the degas bottle which was added later to help address this, though they also point to the tstats being an issue.
Blend door motors can go out leaving hvac stuck on hot or cold. On a dual climate control system, the passenger isn't so bad to replace but the drivers side requires removal of the dash.
Oil and filter needs to be changed every 5k, especially if you keep the DPF of the truck. The regen cycle will dilute the oil with diesel during it's cycle, getting rid of the DPF (and the regen process) with a tuner will extend the life of the engine and prevent this (and add awesome power), also better MPG.
Fuel filters need to be changed every 10k and water separator drained frequently, if you get bad fuel or a little water in the system it's a major repair. Many people install an additional fuel/water separator to try and avoid this.
While not as common EGR coolers can still fail, EGR delete avoids this but will void any warranty and technically make the truck illegal (as will dpf removal).
There are a few places that are known to drip oil, but I haven't heard many instances of it.
Last edited by reighnman; 07-11-2012 at 01:07 PM.